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Microsoft interview questions

Microsoft Interview Questions
Caution: The following are rumored to be MS interview questions. Solving them does not guarantee you a job in Redmond.
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 subarray 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 ]. How about finding both
numbers – the duplicate and the missing?
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 32 bit number.
(caution: looping through testing each bit is not a solution).
10. What are the different ways to say, 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 =x

There is a logical, arithmetic and a datastructure soln to the above
11. Reverse a linked list. (singly-linked, doubly-linked, … ) Can u reverse a singly linked list using only two pointers?
13. In an 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 fundamentals 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 do not know how exactly the books are organized beforehand).
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 (which kind? with a dummy header or without?)

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 chars deleted. (ref. e12.cpp)

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??? Question still remains …

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 optimise 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 interv. was on the Microsoft C team.

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

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

36. Some more bitwise optimization at assembly level

37. Some general questions on Lex Yacc etc.

39. Given an array of characters. How would you reverse it?
How would you reverse it without using indexing in the array
//do not understand the last part of the question
//not using indexes => pointer arithmetic??

40. Given a sequence of characters. How will you convert the lower
case characters to upper case characters. (Try using bit vector
- sol given in the C lib -> typec.h) //anything other than
- //c = c - (‘a’ – ‘A’)??

41. RPC Fundamentals

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

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

45. Give an instance in your life in which u were faced with a problem and you tackled it successfully. (oops!)

46. What is your ideal working environment. ( They usually to hear that u can work in group also.)

47. Why do u think u are smart???

48. Questions on the projects listed on the Resume.

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

50. How long do u want to stay in USA and why?

51. What are your geographical preferences?

52. What are your expectations from the job.

53. 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.

54. Do a breadth first traversal of a tree. (print a tree level by level, each level in a different line)

56. 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).
(Devise at least two different methods)

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).
//make an array out of it

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

62. write C code for deleting an element from a linked list (C++)
traversing a linked list
Efficient way of eliminating duplicates from an array
63. What are various problems unique to distributed databases?

64. declare a void pointer
a) void *ptr;

65. make the pointer aligned to a 4 byte boundary in a efficient manner
a) 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 < c =" getc();" a ="="" 0 =""> a is a power of 2.

8. Infinite.

10. Shivku said this question is garbled thru ages.

11. reverse the pointers till you reach the end and print-and-reverse as you return.

12. Have two 'threads' one at twice the speed of the other traversing the list and see if at anytime they meet.

13. Scan the bytes backward till you reach one with the first bit
set to 0. Now this is either a one byte character or the second
byte of a two byte one. Either way it marks a Character boundary.
Start from there and scan forward to find what the last character is.

14. Flip adjacent bits, then flip adjacent 2 bit sets, then 4-bits
and so on. Each of this swap can be done in constant time using
appropriate masks and shifts.
15. if (a+b) < a or (a+b) < b then overflow has occurred

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 program to print the elements of a very long linked list in ascending order. There may be duplicates in the list. You cannot modify the list or create another one. Memory is tight, speed is not a problem.
//ASK questions like what kind of list, and if templates can be used. If //the ascending relationship is defined, etc.

3. Write a function to reverse a singly linked list, given number of links to reverse. (means, the other part will get lost) or we could save the list
append it to the end of the list, i.e. the old head of the original list)

4. Write a function to convert an int to a string.
(itoa, atoi, etc.)

5. Some weird problem on vector calculus with some transformation matrices
being applied - need paper and pencil to describe it.

6. Given ships travel between points A and B, one every hour leaving from
both ends (simultaneously), how many ships are required (minimum), if the
journey takes 1hr 40 mts. How many ships does each ship encounter in its
journey, and at what times?
Ans 4, 3 at 20 mts, 50 mts and 80 mts.

7. 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.

8. How do you represent an n-ary tree? Write a program to print the nodes
of such a tree in breadth first order. (and use a queue), not efficient
Ans. Sibling and firstchild ptr

1. Consider the base -2 representation of numbers. (-2 instead of usual +2).
Give the condition for a number represented in this form to be positive?
Also, if P(A, B) is a function that takes two 0-1 strings A,B in this
representation, when can we say that P(A,B) returns the sum of these two
numbers? … if the position of the most significant set bit is odd, the number is negative, otherwise, the number is positive. How do u find out the most significant (i.e. left most) signed bit

2. Given a maze with cheese at one place and a mouse at some entrance, write
a program to direct the mouse to cheese correctly. (Assume there is a path).
Following primitives are given: moveforward, turnright, turnleft, iswall?, ischeese?, eatcheese.

3. Given an expression tree with no parentheses in it, write the program
to give equivalent infix expression with parentheses inserted where necessary. (inorder traversal, the main problem is the traversal, not parenthesizing it)

1. A byte has only one of its bits set. Write the code to find out which bit is

2. You have a long tape which contains numbers from 1 to a 1000 randomly
arranged except for one number which is repeated, your task is to determine
which number it is. The condition is the algorithm you choose should be
implementable in linear time and space.

3. How do u detect a loop in a linked list? (devise at least two ways)

4. You have a singly linked list (no prev pointer). Your current pointer pointing to a node x. Write code to delete x. You can have as many temp pointers as you need.

1. Given two sorted linked lists write code to merge them (so that the final list is sorted?).

4. Given an integer use only putchar to print each num of the int out on the
screen (in order). eg: Given an int 247, print: 2, 4, 7.

5. Write a class for a linked list. Give all the member functions that u would
like a linked list to have, i.e., scan, insert, delete, etc.

6. A pic has a bitmap assoc w/ it and a 256 long array of original palettes.
Now we have a change list, where some old colors are mapped onto new
colors. Write the code to change the original palette. Now if the original
bitmap has to be changed, write the code that will scan the pic as well as
the changed palette array. The code shud be O(N) and not O(N^2). The struct
of the original palette may b changed to accomplish this.

7. If a pic is getting built in one window and a dialog box pops up on top
of it and then disappears. How d'u refresh the pic?

8. If x = a and y = b, how to swap the two var values w/o using a tmp var?
Ans: x = a-(x-y) and y = b+(x-y)

1. Write a class for binary trees.

2. Asked to examine a piece of code and figure out the bug. The trick was to know operator precedence; in particular, the ? operator.
3. SQL queries
4. Networks question: binding to a UDP socket, info about BSD sockets, etc.
5. Why manholes are round? Because they are round.

1. U r given an array. Reverse the array
Describe ur algorithm based on memory and speed.
2. U r given an array which is supposed to contain numbers from 0 to N.
Assume that two of the numbers are corrupted and become zero.
How will u find these 2 numbers? [ O(n) solution needed ]
Keep two variables – sum and product, compare with series and factorial of the entire array

3. Tell me about the most interesting projects u have done

Google Placement Paper

Hi friends,
Given below are interview questions.
1. Solve this cryptic equation, realizing of course that values for M and E could be interchanged. No leading zeros are allowed.
This can be solved through systematic application logic. For example, cannot be equal to 0, since . That would make , but , which is not possible.
Here is a slow brute-force method of solution that takes a few minutes on a relatively fast machine:This gives the two solutions
777589 - 188106 == 589483777589 - 188103 == 589486
Here is another solution using Mathematica's Reduce command:
A faster (but slightly more obscure) piece of code is the following:
Faster still using the same approach (and requiring ~300 MB of memory):
Even faster using the same approach (that does not exclude leading zeros in the solution, but that can easily be weeded out at the end):

2. Write a haiku describing possible methods for predicting search traffic seasonality.
Math World’s search engineseemed slowed this May. Undergradsprepping for finals.
11 12 11 2 1 11 1 1 2 2 1What's the next line?
This is the "look and say" sequence in which each term after the first describes the previous term: one 1 (11); two 1s (21); one 2 and one 1 (1211); one 1, one 2, and two 1's (111221); and so on. See the look and say sequence entry on Math World for a complete write-up and the algebraic form of a fascinating related quantity known as Conway's constant.
4. You are in a maze of twisty little passages, all alike. There is a dusty laptop here with a weak wireless connection. There are dull, lifeless gnomes strolling around. What dost thou do?
A) Wander aimlessly, bumping into obstacles until you are eaten by a grue.B) Use the laptop as a digging device to tunnel to the next level.C) Play MPoRPG until the battery dies along with your hopes.D) Use the computer to map the nodes of the maze and discover an exit path.E) Email your resume to Google, tell the lead gnome you quit and find yourself in whole different world [sic].
In general, make a state diagram . However, this method would not work in certain pathological cases such as, say, a fractal maze. For an example of this and commentary, see Ed Pegg's column about state diagrams and mazes .
5. What's broken with UNIX?
Their reproductive capabilities.
How would you fix it?
[This exercise is left to the reader.]
6. On your first day at Google, you discover that your cubicle mate wrote the textbook you used as a primary resource in your first year of graduate school. Do you:
A) Fawn obsequiously and ask if you can have an autograph.B) Sit perfectly still and use only soft keystrokes to avoid disturbing her concentrationC) Leave her daily offerings of granola and English toffee from the food bins.D) Quote your favorite formula from the textbook and explain how it's now your mantra.E) Show her how example 17b could have been solved with 34 fewer lines of code.
[This exercise is left to the reader.]
7. Which of the following expresses Google's over-arching philosophy?
A) "I'm feeling lucky"B) "Don't be evil"C) "Oh, I already fixed that"D) "You should never be more than 50 feet from food"E) All of the above
[This exercise is left to the reader.]
8. How many different ways can you color an icosahedron with one of three colors on each face?
For an asymmetric 20-sided solid, there are possible 3-colorings . For a symmetric 20-sided object, the Polya enumeration theorem can be used to obtain the number of distinct colorings. Here is a concise Mathematica implementation:
What colors would you choose?
[This exercise is left to the reader.]
9. This space left intentionally blank. Please fill it with something that improves upon emptiness.
For nearly 10,000 images of mathematical functions, see The Wolfram Functions Site visualization gallery.
10. On an infinite, two-dimensional, rectangular lattice of 1-ohm resistors, what is the resistance between two nodes that are a knight's move away?
This problem is discussed in J. Cserti's 1999 arXiv preprint. It is also discussed in The Mathematica GuideBook for Symbolics, the forthcoming fourth volume in Michael Trott's GuideBook series, the first two of which were published just last week by Springer-Verlag. The contents for all four GuideBooks, including the two not yet published, are available on the DVD distributed with the first two GuideBooks.
11. It's 2PM on a sunny Sunday afternoon in the Bay Area. You're minutes from the Pacific Ocean, redwood forest hiking trails and world class cultural attractions. What do you do?
[This exercise is left to the reader.]
12. In your opinion, what is the most beautiful math equation ever derived?
There are obviously many candidates. The following list gives ten of the authors' favorites:
1. Archimedes' recurrence formula: , , ,2. Euler formula :3. Euler-Mascheroni constant :4. Riemann hypothesis: and implies5. Gaussian integral: 6. Ramanujan's prime product formula:7. Zeta-regularized product :8. Mandelbrot set recursion:9. BBP formula :10. Cauchy integral formula:
An excellent paper discussing the most beautiful equations in physics is Daniel Z. Freedman's “Some beautiful equations of mathematical physics." Note that the physics view on beauty in equations is less uniform than the mathematical one. To quote the not-necessarily-standard view of theoretical physicist P.A.M. Dirac, "It is more important to have beauty in one's equations than to have them fit experiment."
13.Which of the following is NOT an actual interest group formed by Google employees?
A. Women's basketballB. Buffy fansC. CricketersD. Nobel winnersE. Wine club
[This exercise is left to the reader.]
14. What will be the next great improvement in search technology?
Semantic searching of mathematical formulas. See for work currently underway at Wolfram Research that will be made available in the near future.
15. What is the optimal size of a project team, above which additional members do not contribute productivity equivalent to the percentage increase in the staff size?
A) 1B) 3C) 5D) 11E) 24
[This exercise is left to the reader.]
16. Given a triangle ABC, how would you use only a compass and straight edge to find a point P such that triangles ABP, ACP and BCP have equal perimeters? (Assume that ABC is constructed so that a solution does exist.) This is the isoperimetric point, which is at the center of the larger Soddy circle. It is related to Apollonius' problem. The three tangent circles are easy to construct: The circle around has diameter, which gives the other two circles. A summary of compass and straightedge constructions for the outer Soddy circle can be found in " Apollonius' Problem: A Study of Solutions and Their Connections" by David Gisch and Jason M. Ribando.
17. Consider a function which, for a given whole number n, returns the number of one’s required when writing out all numbers between 0 and n. For example, f (13) =6. Notice that f (1) =1. What is the next largest n such that f(n)=n?
The following Mathematica code computes the difference between [the cumulative number of 1s in the positive integers up to n] and [the value of n itself] as n ranges from 1 to 500,000:
The solution to the problem is then the first position greater than the first at which data equals 0:
Which are the first few terms of sequence A014778 in the On-Line Encyclopedia of Integer Sequences?
Checking by hand confirms that the numbers from 1 to 199981 contain a total of 199981 1s:
18. What is the coolest hack you've ever written?
While there is no "correct" answer, a nice hack for solving the first problem in the SIAM hundred-dollar, hundred-digit challenge can be achieved by converting the limit into the strongly divergent series:
And then using Mathematica's numerical function Sequence Limit to trivially get the correct answer (to six digits),
You must tweak parameters a bit or write your own sequence limit to get all 10 digits.
[Other hacks are left to the reader.]
19. It’s known in refined company, that choosing K things out of N can be done in ways as many as choosing N minus K from N: I pick K, you the remaining.
This simply states the binomial coefficient identity.
Find though a cooler bijection, where you show a knack uncanny, of making your choices contain all K of mine. Oh, for pedantry: let K be no more than half N.
It’s more problematic to disentangle semantic meaning precise from this paragraph of verbiage peculiar.
20. What number comes next in the sequence: 10, 9, 60, 90, 70, 66,?
A) 96B) 1000000000000000000000000000000000\0000000000000000000000000000000000\000000000000000000000000000000000C) Either of the aboveD) None of the above
This can be looked up and found to be sequence A052196 in the On-Line Encyclopedia of Integer Sequences, which gives the largest positive integer whose English name has n letters. For example, the first few terms are ten, nine, sixty, ninety, seventy, sixty-six, ninety-six, …. A more correct sequence might be ten, nine, sixty, googol, seventy, sixty-six, ninety-six, googolplex. And also note, incidentally, that the correct spelling of the mathematical term “googol" differs from the name of the company that made up this aptitude test.
The first few can be computed using the Number Name function in Eric Weinstein’s Math World packages:
A mathematical solution could also be found by fitting a Lagrange interpolating polynomial to the six known terms and extrapolating:
21. In 29 words or fewer, describe what you would strive to accomplish if you worked at Google Labs.
[This exercise is left to the reader.]


Hi friends,
I’m BiIal from Gce Salem. I’m a computer science engineering student. I’ve collected various Google interview questions from my seniors and my staffs for my placement preparation. I think it is useful for u and I’ve just posted them all for u. It will useful for those who prepare for any interviews.If u need any help on programming pls feel free to email me at