MICROSOFT INTERVIEW QUESTIONS

Microsoft Interview Questions
The following are actual questions from actual interviews conducted by
Microsoft employees on the main campus. Microsoft Consultants are
sometimes allowed to have a life, so questions asked of them during
interviews don't really count and aren't listed.

The questions tend to follow some basic themes:
Riddles
Algorithms
Applications
Thinkers

Riddles
Why is a manhole cover round?
How many cars are there in the USA? (A popular variant is "How many gas
stations are there in the USA?")
How many manhole covers are there in the USA?
You've got someone working for you for seven days and a gold bar to pay
them. The gold bar is segmented into seven connected pieces. You must
give them a piece of gold at the end of every day. If you are only
allowed to make two breaks in the gold bar, how do you pay your worker?
One train leaves Los Angeles at 15mph heading for New York. Another
train leaves from New York at 20mph heading for Los Angeles on the same
track. If a bird, flying at 25mph, leaves from Los Angeles at the same
time as the train and flies back and forth between the two trains until
they collide, how far will the bird have traveled?
Imagine a disk spinning like a record player turn table. Half of the
disk is black and the other is white. Assume you have an unlimited number
of color sensors. How many sensors would you have to place around the
disk to determine the direction the disk is spinning? Where would they
be placed?
Imagine an analog clock set to 12 o'clock. Note that the hour and
minute hands overlap. How many times each day do both the hour and minute
hands overlap? How would you determine the exact times of the day that
this occurs?
You have two jars, 50 red marbles and 50 blue marbles. A jar will be
picked at random, and then a marble will be picked from the jar. Placing
all of the marbles in the jars, how can you maximize the chances of a
red marble being picked? What are the exact odds of getting a red marble
using your scheme?
Pairs of primes separated by a single number are called prime pairs.
Examples are 17 and 19. Prove that the number between a prime pair is
always divisible by 6 (assuming both numbers in the pair are greater than
6). Now prove that there are no 'prime triples.'
There is a room with a door (closed) and three light bulbs. Outside the
room there are three switches, connected to the bulbs. You may
manipulate the switches as you wish, but once you open the door you can't
change them. Identify each switch with its bulb.
Suppose you had 8 billiard balls, and one of them was slightly heavier,
but the only way to tell was by putting it on a scale against another.
What's the fewest number of times you'd have to use the scale to find
the heavier ball?
Imagine you are standing in front of a mirror, facing it. Raise your
left hand. Raise your right hand. Look at your reflection. When you raise
your left hand your reflection raises what appears to be his right
hand. But when you tilt your head up, your reflection does too, and does
not appear to tilt his/her head down. Why is it that the mirror appears
to reverse left and right, but not up and down?
You have 4 jars of pills. Each pill is a certain weight, except for
contaminated pills contained in one jar, where each pill is weight + 1.
How could you tell which jar had the contaminated pills in just one
measurement?
The SF Chronicle has a word game where all the letters are scrambled up
and you have to figure out what the word is. Imagine that a scrambled
word is 5 characters long:
How many possible solutions are there?
What if we know which 5 letters are being used?
Develop an algorithm to solve the word.
There are 4 women who want to cross a bridge. They all begin on the
same side. You have 17 minutes to get all of them across to the other
side. It is night. There is one flashlight. A maximum of two people can
cross at one time. Any party who crosses, either 1 or 2 people, must have
the flashlight with them. The flashlight must be walked back and forth,
it cannot be thrown, etc. Each woman walks at a different speed. A pair
must walk together at the rate of the slower woman's pace.

Woman 1: 1 minute to cross
Woman 2: 2 minutes to cross
Woman 3: 5 minutes to cross
Woman 4: 10 minutes to cross


For example if Woman 1 and Woman 4 walk across first, 10 minutes have
elapsed when they get to the other side of the bridge. If Woman 4 then
returns with the flashlight, a total of 20 minutes have passed and you
have failed the mission. What is the order required to get all women
across in 17 minutes? Now, what's the other way?
If you had an infinite supply of water and a 5 quart and 3 quart pail,
how would you measure exactly 4 quarts?
You have a bucket of jelly beans. Some are red, some are blue, and some
green. With your eyes closed, pick out 2 of a like color. How many do
you have to grab to be sure you have 2 of the same?
If you have two buckets, one with red paint and the other with blue
paint, and you take one cup from the blue bucket and poor it into the red
bucket. Then you take one cup from the red bucket and poor it into the
blue bucket. Which bucket has the highest ratio between red and blue?
Prove it mathematically.
Algorithms
What's the difference between a linked list and an array?
Implement a linked list. Why did you pick the method you did?
Implement an algorithm to sort a linked list. Why did you pick the
method you did? Now do it in O(n) time.
Describe advantages and disadvantages of the various stock sorting
algorithms.
Implement an algorithm to reverse a linked list. Now do it without
recursion.
Implement an algorithm to insert a node into a circular linked list
without traversing it.
Implement an algorithm to sort an array. Why did you pick the method
you did?
Implement an algorithm to do wild card string matching.
Implement strstr() (or some other string library function).
Reverse a string. Optimize for speed. Optimize for space.
Reverse the words in a sentence, i.e. "My name is Chris" becomes "Chris
is name My." Optimize for speed. Optimize for space.
Find a substring. Optimize for speed. Optimize for space.
Compare two strings using O(n) time with constant space.
Suppose you have an array of 1001 integers. The integers are in random
order, but you know each of the integers is between 1 and 1000
(inclusive). In addition, each number appears only once in the array, except
for one number, which occurs twice. Assume that you can access each
element of the array only once. Describe an algorithm to find the repeated
number. If you used auxiliary storage in your algorithm, can you find an
algorithm that does not require it?
Count the number of set bits in a number. Now optimize for speed. Now
optimize for size.
Multiple by 8 without using multiplication or addition. Now do the same
with 7.
Add numbers in base n (not any of the popular ones like 10, 16, 8 or 2
-- I hear that Charles Simonyi, the inventor of Hungarian Notation,
favors -2 when asking this question).
Write routines to read and write a bounded buffer.
Write routines to manage a heap using an existing array.
Implement an algorithm to take an array and return one with only unique
elements in it.
Implement an algorithm that takes two strings as input, and returns the
intersection of the two, with each letter represented at most once. Now
speed it up. Now test it.
Implement an algorithm to print out all files below a given root node.
Given that you are receiving samples from an instrument at a constant
rate, and you have constant storage space, how would you design a
storage algorithm that would allow me to get a representative readout of
data, no matter when I looked at it? In other words, representative of the
behavior of the system to date.
How would you find a cycle in a linked list?
Give me an algorithm to shuffle a deck of cards, given that the cards
are stored in an array of ints.
The following asm block performs a common math function, what is it?

cwd xor ax, dx
sub ax, dx
Imagine this scenario:
I/O completion ports are communictaions ports which take handles to
files, sockets, or any other I/O. When a Read or Write is submitted to
them, they cache the data (if necessary), and attempt to take the request
to completion. Upon error or completion, they call a user-supplied
function to let the users application know that that particular request has
completed. They work asynchronously, and can process an unlimited
number of simultaneous requests.
Design the implementation and thread models for I/O completion ports.
Remember to take into account multi-processor machines.
Write a function that takes in a string parameter and checks to see
whether or not it is an integer, and if it is then return the integer
value.
Write a function to print all of the permutations of a string.
Implement malloc.
Write a function to print the Fibonacci numbers.
Write a function to copy two strings, A and B. The last few bytes of
string A overlap the first few bytes of string B.
How would you write qsort?
How would you print out the data in a binary tree, level by level,
starting at the top?
Applications
How can computer technology be integrated in an elevator system for a
hundred story office building? How do you optimize for availability? How
would variation of traffic over a typical work week or floor or time of
day affect this?
How would you implement copy-protection on a control which can be
embedded in a document and duplicated readily via the Internet?
Define a user interface for indenting selected text in a Word document.
Consider selections ranging from a single sentence up through
selections of several pages. Consider selections not currently visible or only
partially visible. What are the states of the new UI controls? How will
the user know what the controls are for and when to use them?
How would you redesign an ATM?
Suppose we wanted to run a microwave oven from the computer. What kind
of software would you write to do this?
What is the difference between an Ethernet Address and an IP address?
How would you design a coffee-machine for an automobile.
If you could add any feature to Microsoft Word, what would it be?
How would you go about building a keyboard for 1-handed users?
How would you build an alarm clock for deaf people?
Thinkers
How are M&Ms made?
If you had a clock with lots of moving mechanical parts, you took it
apart piece by piece without keeping track of the method of how it was
disassembled, then you put it back together and discovered that 3
important parts were not included; how would you go about reassembling the
clock?
If you had to learn a new computer language, how would you go about
doing it?
You have been assigned to design Bill Gates bathroom. Naturally, cost
is not a consideration. You may not speak to Bill.
What was the hardest question asked of you so far today?
If MS told you we were willing to invest $5 million in a start up of
your choice, what business would you start? Why?
If you could gather all of the computer manufacturers in the world
together into one room and then tell them one thing that they would be
compelled to do, what would it be?
Explain a scenario for testing a salt shaker.
If you are going to receive an award in 5 years, what is it for and who
is the audience?
How would you explain how to use Microsoft Excel to your grandma?
Why is it that when you turn on the hot water in any hotel, for
example, the hot water comes pouring out almost instantaneously?
Why do you want to work at Microsoft?
Suppose you go home, enter your house/apartment, hit the light switch,
and nothing happens - no light floods the room. What exactly, in order,
are the steps you would take in determining what the problem was?
Interviewer hands you a black pen and says nothing but "This pen is
red."



========================================================================================================================================================================================

ANALYTICAL QUES

(Avg. of 343 ) : If you had an infinite supply of water and a 5 quart
and 3 quart pail, how would you measure exactly 4 quarts?

Rate it: | View Answers

(Avg. of 122 ) : If you could remove any of the 50 states, which state
would it be and why?

Rate it: | View Answers
(Avg. of 78 ) : If you are on a boat and you throw out a suitcase, will
the level of water increase?

Rate it: | View Answers
(Avg. of 87 ) : There are 3 ants at 3 corners of a triangle, they
randomly start moving towards another corner. What is the probability that
they don't collide?

Rate it: | View Answers
(Avg. of 50 ) : Three men were renting a motel figuring the room cost
30 dollars they would pitch in ten a piece.The room was only 25 so they
each gave the bell boy ten,(tip)the bellboy didn"t think that would be
fair so he gave them each back 1 dollar and kept 2 for himself.What
happened to the other dollar? ( sent by MACsabastion@webtv.net )


++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++==

C++ QUES :

(Avg. of 1423 ) : What is Operator, Operand, Expression, Statement in
'C'?

Rate it: | View Answers

(Avg. of 364 ) : What is polymorphism?

Rate it: | View Answers
(Avg. of 84 ) : What is operator overloading?

Rate it: | View Answers
(Avg. of 55 ) : What are templates?

Rate it: | View Answers
(Avg. of 72 ) : Declare a void pointer.

Rate it: | View Answers
(Avg. of 50 ) : Declare a function pointer which takes a pointer to
char as an argument and returns a void pointer.

Rate it: | View Answers
(Avg. of 31 ) : Type-define a function pointer which takes a int and
float as parameter and returns a float *.

Rate it: | View Answers
(Avg. of 94 ) : What does the following C statement do?
while(*c++ = *d++); assuming c and d are pointers to characters.

Rate it: | View Answers
(Avg. of 52 ) : How do you call a C module within a C++ module.

Rate it: | View Answers
(Avg. of 54 ) : What is the difference between run time binding and
compile time binding? Discuss.

Rate it: | View Answers
(Avg. of 20 ) : Compare and contrast C++ and Java.

Rate it: | View Answers
(Avg. of 23 ) : Why does C/C++ give better run-time performance then
Java?

Rate it: | View Answers
(Avg. of 14 ) : Does C++ come with in-built threading support.

Rate it: | View Answers
(Avg. of 19 ) : Class A derives B derives C. All have foo(). I cast C
to A and call foo(). What happens?

Rate it: | View Answers
(Avg. of 27 ) : All classes A, B, C have default constructor, foo()
that calls parent foo() and allocates 100 bytes to their own private local
variable, and a destructor that frees the 100 bytes. I create a C
object and then destroy it. What's the problem? Did all the memory get
freed? What if I create C, cast to A, and then destroy it. How would I make
sure memory is freed? (destructor must be "virtual" and each destructor
must call parent destructor)

Rate it: | View Answers
(Avg. of 26 ) : What errors are caught at compile time vs link time?

Rate it: | View Answers
(Avg. of 30 ) : What is the value of "a" after this?
int (*a) [10];
a++;

Rate it: | View Answers
(Avg. of 45 ) : What is wrong with this?
main(){
int *ptr;
*ptr=10;
}

Rate it: | View Answers
(Avg. of 39 ) : Given int n, i=10, j=20, x=3, y = 100;
What is the value of n and y at the end of each of the following
expressions?
a) n = (i > j) && (x < ++y);
b) n = (j - i) && (x < y++);
c) n = (i < j) || (y+=i);

Rate it: | View Answers
(Avg. of 34 ) : int x = 5;
int y = 7;
What is the value of x and y after the expression y+=x++;


Rate it: | View Answers
(Avg. of 58 ) : What's the difference between C and C++?

Rate it: | View Answers
(Avg. of 21 ) : What does Public and Private mean in C++

Rate it: | View Answers
(Avg. of 59 ) : Is it possible to keep 2 stacks in a single array, if
one grows from position one of the array, and the other grows from the
last position. Write a procedure PUSH(x,s) that pushes element x onto
stack S, where S is one or the other of these two stacks. Include all
necessary error checks


========================================================================================================================================================================================

JAVA QUESTIONS N ANSWERS

Java Questions & Answers

(Avg. of 487 ) : What is the difference between an Applet and an
Application?

Rate it: | View Answers

(Avg. of 133 ) : What are java beans?

Rate it: | View Answers
(Avg. of 57 ) : What is RMI?

Rate it: | View Answers
(Avg. of 28 ) : What gives java it's "write once and run anywhere"
nature?

Rate it: | View Answers
(Avg. of 33 ) : What are native methods? How do you use them?

Rate it: | View Answers
(Avg. of 26 ) : How does Java inheritance wor?k

Rate it: | View Answers
(Avg. of 58 ) : How many different types of JDBC drivers are present?
Discuss them.

Rate it: | View Answers
(Avg. of 36 ) : What does the "static" keyword mean in front of a
variable? A method? A class? Curly braces {}?

Rate it: | View Answers
(Avg. of 34 ) : Class A subclass B subclass C. All override foo(). I
cast C to A and call foo(). What happens? Can C call A->foo()?

Rate it: | View Answers
(Avg. of 19 ) : Access specifiers: "public", "protected", "private",
nothing?

Rate it: | View Answers
(Avg. of 18 ) : What does the "final" keyword mean in front of a
variable? A method? A class?

Rate it: | View Answers
(Avg. of 28 ) : Does Java have "goto"?

Rate it: | View Answers
(Avg. of 34 ) : Why "bytecode"? Can you reverse-engineer the code from
bytecode?

Rate it: | View Answers
(Avg. of 31 ) : How does exception handling work in Java?

Rate it: | View Answers
(Avg. of 64 ) : Does Java have destructors?

========================================================================================================================================================================================

DATABASES QUES N ANS

What are two methods of retrieving SQL?

Rate it: | View Answers

(Avg. of 588 ) : What cursor type do you use to retrieve multiple
recordsets?

Rate it: | View Answers
(Avg. of 35 ) : What action do you have to perform before retrieving
data from the next result set of a stored procedure?

Rate it: | View Answers
(Avg. of 36 ) : What is the basic form of a SQL statement to read data
out of a table?

Rate it: | View Answers
(Avg. of 29 ) : What structure can you have the database make to speed
up table reads?

Rate it: | View Answers
(Avg. of 16 ) : What is a "join"?

Rate it: | View Answers
(Avg. of 17 ) : What is a "constraint"?

Rate it: | View Answers
(Avg. of 11 ) : What is a "primary key"?

Rate it: | View Answers
(Avg. of 11 ) : What is a "functional dependency"? How does it relate
to database table design?

Rate it: | View Answers
(Avg. of 15 ) : What is a "trigger"?

Rate it: | View Answers
(Avg. of 7 ) : What is "index covering" of a query?

Rate it: | View Answers
(Avg. of 42 ) : What is a SQL view?


========================================================================================================================================================================================

Algorithms & Coding




(Avg. of 188 ) : Write a function to print the Fibonacci numbers.

Rate it: | View Answers

(Avg. of 114 ) : Give a one-line C expression to test whether a number
is a power of 2. Now implement it without using loops.

Rate it: | View Answers
(Avg. of 58 ) : Implement an algorithm to sort a linked list.

Rate it: | View Answers
(Avg. of 66 ) : Reverse a string.

Rate it: | View Answers
(Avg. of 29 ) : Given a linked list which is sorted, how will you
insert in sorted way.

Rate it: | View Answers
(Avg. of 11 ) : Implement an algorithm to insert in a sorted list.

Rate it: | View Answers
(Avg. of 9 ) : Delete an element from a doubly linked list.

Rate it: | View Answers
(Avg. of 14 ) : Implement an algorithm to sort an array.

Rate it: | View Answers
(Avg. of 13 ) : Given a sequence of characters, how will you convert
the lower case characters to upper case characters?

Rate it: | View Answers
(Avg. of 13 ) : Write a routine that prints out a 2-D array in spiral
order.

Rate it: | View Answers
(Avg. of 31 ) : Give a fast way to multiply a number by 7.

Rate it: | View Answers
(Avg. of 10 ) : Write a function that takes in a string parameter and
checks to see whether or not it is an integer, and if it is then return
the integer value.

Rate it: | View Answers
(Avg. of 8 ) : How would you print out the data in a binary tree, level
by level, starting at the top?

Rate it: | View Answers
(Avg. of 13 ) : Write a routine to draw a circle given a center
coordiante (x,y) and a radius (r) without making use of any floating point
computations.

Rate it: | View Answers
(Avg. of 39 ) : Implement a TIC-TAC-TOE game assuming Computer as one
of the player. Optimize it for fast computer play time and space. Do
some analysis on memory and processing requirements .

Rate it: | View Answers
(Avg. of 17 ) : You are given two strings: S1 and S2. Delete from S2
all those characters which occur in S1 also and create a clean S2 with
the relevant characters deleted.

Rate it: | View Answers
(Avg. of 3 ) : Write a small lexical analyzer for expressions like
"a*b" etc.

Rate it: | View Answers
(Avg. of 11 ) : Given an array t[100] which contains numbers between 1
and 99. Return the duplicated value. Try both O(n) and O(n-square).

Rate it: | View Answers
(Avg. of 7 ) : Write efficient code for extracting unique elements from
a sorted list of array.

Rate it: | View Answers
(Avg. of 7 ) : Print an integer using only putchar. Try doing it
without using extra storage.

Rate it: | View Answers
(Avg. of 6 ) : Write a function that allocates memory for a
two-dimensional array of given size(parameter x & y)

Rate it: | View Answers
(Avg. of 7 ) : How would you do conditional compilation ?

Rate it: | View Answers
(Avg. of 19 ) : Write an algorithm to draw a 3D pie chart ?

Rate it: | View Answers
(Avg. of 13 ) : Write a funtion that finds repeating characters in a
string.

Rate it: | View Answers
(Avg. of 11 ) : Write a routine to reverse a series of numbers without
using an array.

Rate it: | View Answers
(Avg. of 12 ) : Write a function to find the nth item from the end of a
linked list in a single pass.

Rate it: | View Answers
(Avg. of 6 ) : Write a function to compute the factorial of a given
integer.

Rate it: | View Answers
(Avg. of 17 ) : Give me an algorithm for telling me the number I didn't
give you in a given range of numbers. (Numbers are given at random)

Rate it: | View Answers
(Avg. of 17 ) : Write a function that finds the last instance of a
character in a string.

Rate it: | View Answers

Try our Advanced Interview Questions and Answers Guide for questions
frequently asked at companies such as Microsoft, SUN Microsystems, Oracle
etc.


Jeeve network sites: Easter Eggs | Goofups | Jeeve Technologies
Add a URL | Contact Us | Frequently as


Rate it: | View Answers
(Avg. of 25 ) : You have b boxes and n dollars. If I want any amount of
money from 0 to n dollars, you must be able to hand me 0 to b boxes so
that I get exactly what I request." The two questions were "What are
the restrictions on b and n, and how is money distributed among the
boxes?

Rate it: | View Answers
(Avg. of 49 ) : What is the sum of the numbers from 1 to 1000?

Rate it: | View Answers
(Avg. of 39 ) : You are an employer. You have ten employees. Each
month, each one of your ten employees gives you ten bags of gold. Each bag
of gold has ten pieces of gold in it. Each piece of gold weighs one
pound. One of your employees is cheating you by only putting nine pieces of
gold in each of his ten bags of gold. You have a scale (not a balance,
a scale), and you can only take one measurement from the scale, only
one (1) reading.

How can you tell which of the ten employees is cheating you by using
this scale and only taking one measurement?

Rate it: | View Answers
(Avg. of 38 ) : How many points are there on the globe where by walking
one mile south, one mile east and one mile north you reach the place
where you started.

Rate it: | View Answers
(Avg. of 23 ) : How would go about finding out where to look for a book
in a library? (You do not know how the books are organized beforehand)

Rate it: | View Answers
(Avg. of 25 ) : Imagine you are standing in front of a mirror, facing
it. Raise your left hand. Raise your right hand. Look at your
reflection. When you raise your left hand your reflection raises what appears to
be his right hand. But when you tilt your head up, your reflection does
too, and does not appear to tilt his/her head down. Why is it that the
mirror appears to reverse left and right, but not up and down?

Rate it: | View Answers
(Avg. of 21 ) : You have a bucket of jelly beans. Some are red, some
are blue, and some green. With your eyes closed, pick out 2 of a like
color. How many do you have to grab to be sure you have 2 of the same?

Rate it: | View Answers
(Avg. of 18 ) : You are given a scale which you are to use to measure
eight balls. Seven of these balls have the same weight: the eigth ball
is heavier than the rest. What is the minimum number of weighs you could
perform to find the heaviest of the eight balls?. Remmber it's a scale
not a balance. (i.e. It can just tell you if one side is heavier than
the other it can't give you the exact weight).

Rate it: | View Answers
(Avg. of 13 ) : How would you design a toaster?

Rate it: | View Answers
(Avg. of 10 ) : How would you design an universal remote control?

Rate it: | View Answers
(Avg. of 22 ) : How would you design a clock for a blind person?

Rate it: | View Answers
(Avg. of 30 ) : How many miles of road are there in the US

Rate it: | View Answers
(Avg. of 64 ) : There are n couples attending a party. Each one shakes
hands with the persons he doesn't know. (Assuming each person knows
his/her partner) Mary and John are a couple. John asked the rest of the
party-attenders how many times he has shaken hands. Each one gives a
unique answer. How many times does Mary shake hands?


Plain Text Attachment [ Download File | Save to Yahoo! Briefcase ]

Interview Questions - Microsoft, etc.
Disclaimer: This page is in no way connected with Microsoft
Corporation, its affiliates, friends or haters

What?

Here is a set of questions that I have with me which software guys have
asked at interviews in the past, most of them are actually from
Microsoft but a few have been pulled together from other places too. I have
collected these from friends and would welcome any additions from you.
Mail them to kiran AT usc DOT edu. Do send me your solutions, but the
intent of this page is to kindle enough interest in you to try similar
logic and programming questions.
PLEASE DO NOT REQUEST ME FOR MORE SOLUTIONS!

Why?

I have grown up reading Martin Gardner's Scientific American columns on
Mathematical Games and interesting mathematics olympiad problems in
high school. I discovered, to my delight, Bentley's Programming Pearls and
David Gries' The Science of Programming in my computer science
education. There is underlying beauty in mathematics and computer science. Some
find it and others hate the subjects. When I found some of the
Microsoft interview questions in graduate school, they were similar to
mathematical puzzles that I was interested in. I started collecting them more
as an illustration of interesting logic puzzles and algorithms in
programming, than as an interview aid. If it has morphed into an interview
questions page, that is more due to interest from all interviewees out
there.

Some of the programming questions have a basic foundation in
mathematics and algorithms. If the given data structure has a specific amount of
information and the question asks you to extract/modify the given
information, it is possible (though not always obvious) to find optimal
solutions, and prove that it cannot be done any better, by quantifying the
information content. But, there are always elegant and ugly ways to
extract the same information. When you manage to find out the optimal
solution to a problem, it usually not only turns out to be elegant, but
also has the "aha!" factor to it. Try proving on paper the following
question from my undergraduate mid-term:

1. Everyone Loves All Lovers
2. Romeo Loves Juliet
Therefore, prove (i.e. 1 AND 2 => 3)
3. I Love You


How?

To answer one of the more frequent questions that I get: No! I have
never interviewed at Microsoft. In fact, I work in a microprocessor
company far removed from any software development (though I work mostly in
programming). However, I have had two of my roommates and two more
housemates eventually working in Microsoft, in addition to a large number of
friends. None of them have contributed to this page AFTER they started
working at Microsoft. Microsoft itself does not hold any patents and
nor has it invented most of the questions. Most of them come from
mathematics and physics books, party puzzles, programming lore and standard
textbooks. I know many companies ask similar questions, though Microsoft
might have made the practice more common (especially with the manhole
cover type of questions).

Usage

I have spent some time in collecting with the intention of their value
as a practice session. They are not meant to be exact questions that
you need to know and answer in an interview. They are supposed to make
you think! Discuss with your friends, colleagues, professors for answers
(get your tuition money's worth). I have left the page in simple text
format so you can print them out and try them on your flight to the
interview in case you are pressed for time. One of the strangest phone
calls I remember is from a girl, staying up in a Microsoft provided hotel
room in Redmond the night before the interview, asking me about the
solution for one of the questions from this page. I hope the rest of you
are saner (or do not have my phone number).

Kiran Bondalapati

Ze Meat

Puzzles, Riddles, etc.
Programming Questions
Computer Networks, Databases, etc.
Computer Architecture

Puzzles, Riddles and Others

0. Classic: If a bear walks one mile south, turns left and walks one
mile to the east and then turns left again and walks one mile north and
arrives at its original position, what is the color of the bear.

ANS. The color of the bear is trivial. The possible solutions to it are
interesting. In addition to the trivial north pole, there are
additional circles near south pole. Think it out.

* 1. Given a rectangular (cuboidal for the puritans) cake with a
rectangular piece removed (any size or orientation), how would you cut the
remainder of the cake into two equal halves with one straight cut of a
knife?

ANS. Join the centers of the original and the removed rectangle. It
works for cuboids too! BTW, I have been getting many questions asking why
a horizontal slice across the middle will not do. Please note the "any
size or orientation" in the question! Don't get boxed in by the way you
cut your birthday cake :) Think out of the box.

2. There are 3 baskets. one of them have apples, one has oranges only
and the other has mixture of apples and oranges. The labels on their
baskets always lie. (i.e. if the label says oranges, you are sure that it
doesn't have oranges only,it could be a mixture) The task is to pick
one basket and pick only one fruit from it and then correctly label all
the three baskets.

HINT. There are only two combinations of distributions in which ALL the
baskets have wrong labels. By picking a fruit from the one labeled
MIXTURE, it is possible to tell what the other two baskets have.

3. You have 8 balls. One of them is defective and weighs less than
others. You have a balance to measure balls against each other. In 2
weighings how do you find the defective one?

4. Why is a manhole cover round?

HINT. The diagonal of a square hole is larger than the side of a cover!

Alternate answers: 1. Round covers can be transported by one person,
because they can be rolled on their edge. 2. A round cover doesn't need
to be rotated to fit over a hole.

5. How many cars are there in the USA?

6. You've got someone working for you for seven days and a gold bar to
pay them. The gold bar is segmented into seven connected pieces. You
must give them a piece of gold at the end of every day. If you are only
allowed to make two breaks in the gold bar, how do you pay your worker?

7. One train leaves Los Angeles at 15mph heading for New York. Another
train leaves from New York at 20mph heading for Los Angeles on the same
track. If a bird, flying at 25mph, leaves from Los Angeles at the same
time as the train and flies back and forth between the two trains until
they collide, how far will the bird have traveled?

HINT. Think relative speed of the trains.

8. You have two jars, 50 red marbles and 50 blue marbles. A jar will be
picked at random, and then a marble will be picked from the jar.
Placing all of the marbles in the jars, how can you maximize the chances of a
red marble being picked? What are the exact odds of getting a red
marble using your scheme?

9. Imagine you are standing in front of a mirror, facing it. Raise your
left hand. Raise your right hand. Look at your reflection. When you
raise your left hand your reflection raises what appears to be his right
hand. But when you tilt your head up, your reflection does too, and does
not appear to tilt his/her head down. Why is it that the mirror appears
to reverse left and right, but not up and down?

10. You have 5 jars of pills. Each pill weighs 10 gram, except for
contaminated pills contained in one jar, where each pill weighs 9 gm. Given
a scale, how could you tell which jar had the contaminated pills in
just one measurement?

ANS. 1. Mark the jars with numbers 1, 2, 3, 4, and 5.
2. Take 1 pill from jar 1, take 2 pills from jar 2, take 3 pills from
jar 3, take 4 pills from jar 4 and take 5 pills from jar 5.
3. Put all of them on the scale at once and take the measurement.
4. Now, subtract the measurement from 150 ( 1*10 + 2*10 + 3*10 + 4*10 +
5*10)
5. The result will give you the jar number which has contaminated pill.

11. If you had an infinite supply of water and a 5 quart and 3 quart
pail, how would you measure exactly 4 quarts?

12. You have a bucket of jelly beans. Some are red, some are blue, and
some green. With your eyes closed, pick out 2 of a like color. How many
do you have to grab to be sure you have 2 of the same?

13. Which way should the key turn in a car door to unlock it?

14. If you could remove any of the 50 states, which state would it be
and why?

15. There are four dogs/ants/people at four corners of a square of unit
distance. At the same instant all of them start running with unit speed
towards the person on their clockwise direction and will always run
towards that target. How long does it take for them to meet and where?

HINT. They will meet in the center and the distance covered by them is
independent of the path they actually take (a spiral).

16. (from Tara Hovel) A helicopter drops two trains, each on a
parachute, onto a straight infinite railway line. There is an undefined
distance between the two trains. Each faces the same direction, and upon
landing, the parachute attached to each train falls to the ground next to
the train and detaches. Each train has a microchip that controls its
motion. The chips are identical. There is no way for the trains to know
where they are. You need to write the code in the chip to make the trains
bump into each other. Each line of code takes a single clock cycle to
execute.
You can use the following commands (and only these);
MF - moves the train forward
MB - moves the train backward
IF (P) - conditional that's satisfied if the train is next to a
parachute. There is no "then" to this IF statement.
GOTO


ANS.
A: MF
IF (P)
GOTO B
GOTO A
-----
B: MF
GOTO B
Explanation: The first line simply gets them off the parachutes. You
need to get the trains off their parachutes so the back train can find
the front train's parachute, creating a special condition that will allow
it to break out of the code they both have to follow initially. They
both loop through A: until the back train finds the front train's
parachute, at which point it goes to B: and gets stuck in that loop. The front
train still hasn't found a parachute, so it keeps in the A loop.
Because each line of code takes a "clock cycle" to execute, it takes longer
to execute the A loop than the B loop, therefore the back train (running
in the B loop) will catch up to the front train.
Personality
It is best to read some website or a book for questions like these.

1. Tell me the courses you liked and why did you like them.

2. Give an instance in your life in which you were faced with a problem
and you tackled it successfully.

3. What is your ideal working environment.

4. Why do you think you are smart.

5. Questions on the projects listed on the Resume.

6. Do you want to know any thing about the company.( Try to ask some
relevant and interesting question).

7. How long do you want to stay in USA and why (I guess non-citizens
get this)?

8. What is your geographical preference?

9. What are your expectations from the job.

Algorithms and Programming

1. Given a rectangular (cuboidal for the puritans) cake with a
rectangular piece removed (any size or orientation), how would you cut the
remainder of the cake into two equal halves with one straight cut of a
knife ?

2. You're given an array containing both positive and negative integers
and required to find the sub-array with the largest sum (O(N) a la
KBL). Write a routine in C for the above.

3. Given an array of size N in which every number is between 1 and N,
determine if there are any duplicates in it. You are allowed to destroy
the array if you like. [ I ended up giving about 4 or 5 different
solutions for this, each supposedly better than the others ].

4. Write a routine to draw a circle (x ** 2 + y ** 2 = r ** 2) without
making use of any floating point computations at all. [ This one had me
stuck for quite some time and I first gave a solution that did have
floating point computations ].

5. Given only putchar (no sprintf, itoa, etc.) write a routine putlong
that prints out an unsigned long in decimal. [ I gave the obvious
solution of taking % 10 and / 10, which gives us the decimal value in
reverse order. This requires an array since we need to print it out in the
correct order. The interviewer wasn't too pleased and asked me to give a
solution which didn't need the array ].

6. Give a one-line C expression to test whether a number is a power of
2. [No loops allowed - it's a simple test.]

7. Given an array of characters which form a sentence of words, give an
efficient algorithm to reverse the order of the words (not characters)
in it.

8. How many points are there on the globe where by walking one mile
south, one mile east and one mile north you reach the place where you
started.

9. Give a very good method to count the number of ones in a "n" (e.g.
32) bit number.

ANS. Given below are simple solutions, find a solution that does it in
log (n) steps.


Iterative

function iterativecount (unsigned int n)
begin
int count=0;
while (n)
begin
count += n & 0x1 ;
n >>= 1;
end
return count;
end

Sparse Count

function sparsecount (unsigned int n)
begin
int count=0;
while (n)
begin
count++;
n &= (n-1);
end
return count ;
end

10. What are the different ways to implement a condition where the
value of x can be either a 0 or a 1. Apparently the if then else solution
has a jump when written out in assembly. if (x == 0) y=a else y=b There
is a logical, arithmetic and a data structure solution to the above
problem.

11. Reverse a linked list.

12. Insert in a sorted list

13. In a X's and 0's game (i.e. TIC TAC TOE) if you write a program for
this give a fast way to generate the moves by the computer. I mean this
should be the fastest way possible.

The answer is that you need to store all possible configurations of the
board and the move that is associated with that. Then it boils down to
just accessing the right element and getting the corresponding move for
it. Do some analysis and do some more optimization in storage since
otherwise it becomes infeasible to get the required storage in a DOS
machine.

14. I was given two lines of assembly code which found the absolute
value of a number stored in two's complement form. I had to recognize what
the code was doing. Pretty simple if you know some assembly and some
fundaes on number representation.

15. Give a fast way to multiply a number by 7.

16. How would go about finding out where to find a book in a library.
(You don't know how exactly the books are organized beforehand).

17. Linked list manipulation.

18. Tradeoff between time spent in testing a product and getting into
the market first.

19. What to test for given that there isn't enough time to test
everything you want to.

20. First some definitions for this problem: a) An ASCII character is
one byte long and the most significant bit in the byte is always '0'. b)
A Kanji character is two bytes long. The only characteristic of a Kanji
character is that in its first byte the most significant bit is '1'.

Now you are given an array of a characters (both ASCII and Kanji) and,
an index into the array. The index points to the start of some
character. Now you need to write a function to do a backspace (i.e. delete the
character before the given index).

21. Delete an element from a doubly linked list.

22. Write a function to find the depth of a binary tree.

23. Given two strings S1 and S2. Delete from S2 all those characters
which occur in S1 also and finally create a clean S2 with the relevant
characters deleted.

24. Assuming that locks are the only reason due to which deadlocks can
occur in a system. What would be a foolproof method of avoiding
deadlocks in the system.

25. Reverse a linked list.

Ans: Possible answers -

iterative loop
curr->next = prev;
prev = curr;
curr = next;
next = curr->next
endloop

recursive reverse(ptr)
if (ptr->next == NULL)
return ptr;
temp = reverse(ptr->next);
temp->next = ptr;
return ptr;
end


26. Write a small lexical analyzer - interviewer gave tokens.
expressions like "a*b" etc.

27. Besides communication cost, what is the other source of
inefficiency in RPC? (answer : context switches, excessive buffer copying). How
can you optimize the communication? (ans : communicate through shared
memory on same machine, bypassing the kernel _ A Univ. of Wash. thesis)

28. Write a routine that prints out a 2-D array in spiral order!

29. How is the readers-writers problem solved? - using semaphores/ada
.. etc.

30. Ways of optimizing symbol table storage in compilers.

31. A walk-through through the symbol table functions, lookup()
implementation etc. - The interviewer was on the Microsoft C team.

32. A version of the "There are three persons X Y Z, one of which
always lies".. etc..

33. There are 3 ants at 3 corners of a triangle, they randomly start
moving towards another corner.. what is the probability that they don't
collide.

34. Write an efficient algorithm and C code to shuffle a pack of
cards.. this one was a feedback process until we came up with one with no
extra storage.

35. The if (x == 0) y = 0 etc..

36. Some more bitwise optimization at assembly level

37. Some general questions on Lex, Yacc etc.

38. Given an array t[100] which contains numbers between 1..99. Return
the duplicated value. Try both O(n) and O(n-square).

39. Given an array of characters. How would you reverse it. ? How would
you reverse it without using indexing in the array.

40. Given a sequence of characters. How will you convert the lower case
characters to upper case characters. ( Try using bit vector - solutions
given in the C lib -typec.h)

41. Fundamentals of RPC.

42. Given a linked list which is sorted. How will u insert in sorted
way.

43. Given a linked list How will you reverse it.

44. Give a good data structure for having n queues ( n not fixed) in a
finite memory segment. You can have some data-structure separate for
each queue. Try to use at least 90% of the memory space.

45. Do a breadth first traversal of a tree.

46. Write code for reversing a linked list.

47. Write, efficient code for extracting unique elements from a sorted
list of array. e.g. (1, 1, 3, 3, 3, 5, 5, 5, 9, 9, 9, 9) -> (1, 3, 5,
9).

48. Given an array of integers, find the contiguous sub-array with the
largest sum.

ANS. Can be done in O(n) time and O(1) extra space. Scan array from 1
to n. Remember the best sub-array seen so far and the best sub-array
ending in i.

49. Given an array of length N containing integers between 1 and N,
determine if it contains any duplicates.

ANS. [Is there an O(n) time solution that uses only O(1) extra space
and does not destroy the original array?]

50. Sort an array of size n containing integers between 1 and K, given
a temporary scratch integer array of size K.

ANS. Compute cumulative counts of integers in the auxiliary array. Now
scan the original array, rotating cycles! [Can someone word this more
nicely?]

* 51. An array of size k contains integers between 1 and n. You are
given an additional scratch array of size n. Compress the original array
by removing duplicates in it. What if k << n?

ANS. Can be done in O(k) time i.e. without initializing the auxiliary
array!

52. An array of integers. The sum of the array is known not to overflow
an integer. Compute the sum. What if we know that integers are in 2's
complement form?

ANS. If numbers are in 2's complement, an ordinary looking loop like
for(i=total=0;i< n;total+=array[i++]); will do. No need to check for
overflows!

53. An array of characters. Reverse the order of words in it.

ANS. Write a routine to reverse a character array. Now call it for the
given array and for each word in it.

* 54. An array of integers of size n. Generate a random permutation of
the array, given a function rand_n() that returns an integer between 1
and n, both inclusive, with equal probability. What is the expected
time of your algorithm?

ANS. "Expected time" should ring a bell. To compute a random
permutation, use the standard algorithm of scanning array from n downto 1,
swapping i-th element with a uniformly random element <= i-th. To compute a
uniformly random integer between 1 and k (k < n), call rand_n()
repeatedly until it returns a value in the desired range.

55. An array of pointers to (very long) strings. Find pointers to the
(lexicographically) smallest and largest strings.

ANS. Scan array in pairs. Remember largest-so-far and smallest-so-far.
Compare the larger of the two strings in the current pair with
largest-so-far to update it. And the smaller of the current pair with the
smallest-so-far to update it. For a total of <= 3n/2 strcmp() calls. That's
also the lower bound.

56. Write a program to remove duplicates from a sorted array.

ANS. int remove_duplicates(int * p, int size)
{
int current, insert = 1;
for (current=1; current < size; current++)
if (p[current] != p[insert-1])
{
p[insert] = p[current];
current++;
insert++;
} else
current++;

return insert;

}

57. C++ ( what is virtual function ? what happens if an error occurs in
constructor or destructor. Discussion on error handling, templates,
unique features of C++. What is different in C++, ( compare with unix).

58. Given a list of numbers ( fixed list) Now given any other list, how
can you efficiently find out if there is any element in the second list
that is an element of the first list (fixed list).

59. Given 3 lines of assembly code : find it is doing. IT was to find
absolute value.

60. If you are on a boat and you throw out a suitcase, Will the level
of water increase.

61. Print an integer using only putchar. Try doing it without using
extra storage.

62. Write C code for (a) deleting an element from a linked list (b)
traversing a linked list

63. What are various problems unique to distributed databases

64. Declare a void pointer ANS. void *ptr;

65. Make the pointer aligned to a 4 byte boundary in a efficient manner
ANS. Assign the pointer to a long number and the number with 11...1100
add 4 to the number

66. What is a far pointer (in DOS)

67. What is a balanced tree

68. Given a linked list with the following property node2 is left child
of node1, if node2 < node1 else, it is the right child.

O P
|
|
O A
|
|
O B
|
|
O C

How do you convert the above linked list to the form without disturbing
the property. Write C code for that.


O P
|
|
O B
/ \
/ \
/ \
O ? O ?

determine where do A and C go

69. Describe the file system layout in the UNIX OS

ANS. describe boot block, super block, inodes and data layout

70. In UNIX, are the files allocated contiguous blocks of data

ANS. no, they might be fragmented

How is the fragmented data kept track of

ANS. Describe the direct blocks and indirect blocks in UNIX file system

71. Write an efficient C code for 'tr' program. 'tr' has two command
line arguments. They both are strings of same length. tr reads an input
file, replaces each character in the first string with the corresponding
character in the second string. eg. 'tr abc xyz' replaces all 'a's by
'x's, 'b's by 'y's and so on. ANS.
a) have an array of length 26.
put 'x' in array element corr to 'a'
put 'y' in array element corr to 'b'
put 'z' in array element corr to 'c'
put 'd' in array element corr to 'd'
put 'e' in array element corr to 'e'
and so on.

the code
while (!eof)
{
c = getc();
putc(array[c - 'a']);
}

72. what is disk interleaving

73. why is disk interleaving adopted

74. given a new disk, how do you determine which interleaving is the
best a) give 1000 read operations with each kind of interleaving
determine the best interleaving from the statistics

75. draw the graph with performance on one axis and 'n' on another,
where 'n' in the 'n' in n-way disk interleaving. (a tricky question,
should be answered carefully)

76. I was a c++ code and was asked to find out the bug in that. The bug
was that he declared an object locally in a function and tried to
return the pointer to that object. Since the object is local to the
function, it no more exists after returning from the function. The pointer,
therefore, is invalid outside.

77. A real life problem - A square picture is cut into 16 squares and
they are shuffled. Write a program to rearrange the 16 squares to get
the original big square.

78.
int *a;
char *c;
*(a) = 20;
*c = *a;
printf("%c",*c);

what is the output?

79. Write a program to find whether a given m/c is big-endian or
little-endian!

80. What is a volatile variable?

81. What is the scope of a static function in C ?

82. What is the difference between "malloc" and "calloc"?

83. struct n { int data; struct n* next}node;
node *c,*t;
c->data = 10;
t->next = null;
*c = *t;
what is the effect of the last statement?

84. If you're familiar with the ? operator x ? y : z
you want to implement that in a function: int cond(int x, int y, int
z); using only ~, !, ^, &, +, |, <<, >> no if statements, or loops or
anything else, just those operators, and the function should correctly
return y or z based on the value of x. You may use constants, but only 8
bit constants. You can cast all you want. You're not supposed to use
extra variables, but in the end, it won't really matter, using vars just
makes things cleaner. You should be able to reduce your solution to a
single line in the end though that requires no extra vars.

85. You have an abstract computer, so just forget everything you know
about computers, this one only does what I'm about to tell you it does.
You can use as many variables as you need, there are no negative
numbers, all numbers are integers. You do not know the size of the integers,
they could be infinitely large, so you can't count on truncating at any
point. There are NO comparisons allowed, no if statements or anything
like that. There are only four operations you can do on a variable.
1) You can set a variable to 0.
2) You can set a variable = another variable.
3) You can increment a variable (only by 1), and it's a post increment.
4) You can loop. So, if you were to say loop(v1) and v1 = 10, your loop
would execute 10 times, but the value in v1 wouldn't change so the
first line in the loop can change value of v1 without changing the number
of times you loop.
You need to do 3 things.
1) Write a function that decrements by 1.
2) Write a function that subtracts one variable from another.
3) Write a function that divides one variable by another.
4) See if you can implement all 3 using at most 4 variables. Meaning,
you're not making function calls now, you're making macros. And at most
you can have 4 variables. The restriction really only applies to
divide, the other 2 are easy to do with 4 vars or less. Division on the other
hand is dependent on the other 2 functions, so, if subtract requires 3
variables, then divide only has 1 variable left unchanged after a call
to subtract. Basically, just make your function calls to decrement and
subtract so you pass your vars in by reference, and you can't declare
any new variables in a function, what you pass in is all it gets.
Linked lists

* 86. Under what circumstances can one delete an element from a singly
linked list in constant time?

ANS. If the list is circular and there are no references to the nodes
in the list from anywhere else! Just copy the contents of the next node
and delete the next node. If the list is not circular, we can delete
any but the last node using this idea. In that case, mark the last node
as dummy!

* 87. Given a singly linked list, determine whether it contains a loop
or not.

ANS. (a) Start reversing the list. If you reach the head, gotcha! there
is a loop!
But this changes the list. So, reverse the list again.
(b) Maintain two pointers, initially pointing to the head. Advance one
of them one node at a time. And the other one, two nodes at a time. If
the latter overtakes the former at any time, there is a loop!

p1 = p2 = head;

do {
p1 = p1->next;
p2 = p2->next->next;
} while (p1 != p2);

88. Given a singly linked list, print out its contents in reverse
order. Can you do it without using any extra space?

ANS. Start reversing the list. Do this again, printing the contents.

89. Given a binary tree with nodes, print out the values in
pre-order/in-order/post-order without using any extra space.

90. Reverse a singly linked list recursively. The function prototype is
node * reverse (node *) ;

ANS.

node * reverse (node * n)
{
node * m ;

if (! (n && n -> next))
return n ;

m = reverse (n -> next) ;
n -> next -> next = n ;
n -> next = NULL ;
return m ;
}

91. Given a singly linked list, find the middle of the list.

HINT. Use the single and double pointer jumping. Maintain two pointers,
initially pointing to the head. Advance one of them one node at a time.
And the other one, two nodes at a time. When the double reaches the
end, the single is in the middle. This is not asymptotically faster but
seems to take less steps than going through the list twice.

Bit-manipulation

92. Reverse the bits of an unsigned integer.

ANS.

#define reverse(x) \
(x=x>>16|(0x0000ffff&x)<<16, \
x=(0xff00ff00&x)>>8|(0x00ff00ff&x)<<8, \
x=(0xf0f0f0f0&x)>>4|(0x0f0f0f0f&x)<<4, \
x=(0xcccccccc&x)>>2|(0x33333333&x)<<2, \
x=(0xaaaaaaaa&x)>>1|(0x55555555&x)<<1)

* 93. Compute the number of ones in an unsigned integer.

ANS.

#define count_ones(x) \
(x=(0xaaaaaaaa&x)>>1+(0x55555555&x), \
x=(0xcccccccc&x)>>2+(0x33333333&x), \
x=(0xf0f0f0f0&x)>>4+(0x0f0f0f0f&x), \
x=(0xff00ff00&x)>>8+(0x00ff00ff&x), \
x=x>>16+(0x0000ffff&x))

94. Compute the discrete log of an unsigned integer.

ANS.

#define discrete_log(h) \
(h=(h>>1)|(h>>2), \
h|=(h>>2), \
h|=(h>>4), \
h|=(h>>8), \
h|=(h>>16), \
h=(0xaaaaaaaa&h)>>1+(0x55555555&h), \
h=(0xcccccccc&h)>>2+(0x33333333&h), \
h=(0xf0f0f0f0&h)>>4+(0x0f0f0f0f&h), \
h=(0xff00ff00&h)>>8+(0x00ff00ff&h), \
h=(h>>16)+(0x0000ffff&h))
If I understand it right, log2(2) =1, log2(3)=1, log2(4)=2..... But
this macro does not work out log2(0) which does not exist! How do you
think it should be handled?

* 95. How do we test most simply if an unsigned integer is a power of
two?

ANS. #define power_of_two(x) \ ((x)&&(~(x&(x-1))))

96. Set the highest significant bit of an unsigned integer to zero.

ANS. (from Denis Zabavchik) Set the highest significant bit of an
unsigned integer to zero
#define zero_most_significant(h) \
(h&=(h>>1)|(h>>2), \
h|=(h>>2), \
h|=(h>>4), \
h|=(h>>8), \
h|=(h>>16))

97. Let f(k) = y where k is the y-th number in the increasing sequence
of non-negative integers with the same number of ones in its binary
representation as y, e.g. f(0) = 1, f(1) = 1, f(2) = 2, f(3) = 1, f(4) =
3, f(5) = 2, f(6) = 3 and so on. Given k >= 0, compute f(k).

Others

98. A character set has 1 and 2 byte characters. One byte characters
have 0 as the first bit. You just keep accumulating the characters in a
buffer. Suppose at some point the user types a backspace, how can you
remove the character efficiently. (Note: You cant store the last
character typed because the user can type in arbitrarily many backspaces)

99. What is the simples way to check if the sum of two unsigned
integers has resulted in an overflow.

100. How do you represent an n-ary tree? Write a program to print the
nodes of such a tree in breadth first order.

101. Write the 'tr' program of UNIX. Invoked as

tr -str1 -str2. It reads stdin and prints it out to stdout, replacing
every occurance of str1[i] with str2[i].

e.g. tr -abc -xyz
to be and not to be <- input
to ye xnd not to ye <- output



Networks and Security

1. How do you use RSA for both authentication and secrecy?

2. What is ARP and how does it work?

3. What's the difference between a switch and a router?

4. Name some routing protocols? (RIP,OSPF etc..)

5. How do you do authentication with message digest(MD5)? (Usually MD
is used for finding tampering of data)

6. How do you implement a packet filter that distinguishes following
cases and selects first case and rejects second case.

i) A host inside the corporate n/w makes a ftp request to outside host
and the outside host sends reply.

ii) A host outside the network sends a ftp request to host inside. for
the packet filter in both cases the source and destination fields will
look the same.

7. How does traceroute work? Now how does traceroute make sure that the
packet follows the same path that a previous (with ttl - 1) probe
packet went in?

8. Explain Kerberos Protocol ?

9. What are digital signatures and smart cards?

10. Difference between discretionary access control and mandatory
access control?

Java

1. How do you find the size of a java object (not the primitive type) ?

ANS. type cast it to string and find its s.length()

2. Why is multiple inheritance not provided in Java?

3. Thread t = new Thread(); t.start(); t = null; now what will happen
to the created thread?

4. How is garbage collection done in java?

5. How do you write a "ping" routine in java?

6. What are the security restrictions on applets?
Graphics

1. Write a function to check if two rectangles defined as below overlap
or not. struct rect { int top, bot, left, right; } r1, r2;

2. Write a SetPixel(x, y) function, given a pointer to the bitmap. Each
pixel is represented by 1 bit. There are 640 pixels per row. In each
byte, while the bits are numbered right to left, pixels are numbered left
to right. Avoid multiplications and divisions to improve performance.

Databases

* 1. You, a designer want to measure disk traffic i.e. get a histogram
showing the relative frequency of I/O/second for each disk block. The
buffer pool has b buffers and uses LRU replacement policy. The disk
block size and buffer pool block sizes are the same. You are given a
routine int lru_block_in_position (int i) which returns the block_id of the
block in the i-th position in the list of blocks managed by LRU. Assume
position 0 is the hottest. You can repeatedly call this routine. How
would you get the histogram you desire?

Hints and Answers

1. Simply do histogram [lru_block_in_position (b-1)] ++ at frequent
intervals... The sampling frequency should be close to the disk I/O rate.
It can be adjusted by remembering the last block seen in position b. If
same, decrease frequency; if different, increase, with exponential
decay etc. And of course, take care of overflows in the histogram.

Semaphores

1. Implement a multiple-reader-single-writer lock given a
compare-and-swap instruction. Readers cannot overtake waiting writers.

Computer Architecture
1. Explain what is DMA?
2. What is pipelining?
3. What are superscalar machines and vliw machines?
4. What is cache?
5. What is cache coherency and how is it eliminated?
6. What is write back and write through caches?
7. What are different pipelining hazards and how are they eliminated.
8. What are different stages of a pipe?
9. Explain more about branch prediction in controlling the control
hazards
10. Give examples of data hazards with pseudo codes.
11. How do you calculate the number of sets given its way and size in a
cache?
12. How is a block found in a cache?
13. Scoreboard analysis.
14. What is miss penalty and give your own ideas to eliminate it.
15. How do you improve the cache performance.
16. Different addressing modes.
17. Computer arithmetic with two's complements.
18. About hardware and software interrupts.
19. What is bus contention and how do you eliminate it.
20. What is aliasing?
21) What is the difference between a latch and a flip flop?
22) What is the race around condition? How can it be overcome?
23) What is the purpose of cache? How is it used?
24) What are the types of memory management?
Kiran Bondalapati Homepage