MICROSOFT QUESTION BANK Here is a set of questions that I have with me which MSFT guys have asked at interviews in the past. 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 ]. 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=0 else y =x There is a logical, arithmetic and a datastructure soln 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 gast way to generate the moves by the computer. I mean this should be the fasteset 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. 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.. 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 algo 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 - sol given in the C lib -> typec.h) 41. Fundas 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. 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. 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 preference? 52. What are your expecctations 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. 55. Write code for reversing a linked list. 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). 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 deleting an element from a linked listy traversing a linked list efficient way of elimiating 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 < node1 els, 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 a) describe boot block, super block, inodes and data layout 70. In UNIX, are the files allocated contiguous blocks of data a) no, they might be fragmented how is the fragmented data kept track of a) 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. 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 performace 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 sqaures and they are shuffled. Write a program to rearrange the 16 squares to get the original big square. Some of the Questions asked in Msoft interviews: (so: ACN, Shivku and Guhan) - -------------------------------------------------- These are some of the questions asked by Microsoft. This might interest some of you who are interviewing with them. I have some more questions which Ill compile and send them to you. Do make good use of it and all the best. If you have any additional add them to this and send 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 ? 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 ]. 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=0 else y =x There is a logical, arithmetic and a datastructure soln to the above problem. -- Thats all for now. 6. (a-1) xor a == 0 => a is a power of 2. 11. How can you print singly linked list in reverse order? (it's a huge list and you cant use recursion) 12. How can you find out if there is a loop in a very long list? 13. 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) 14. How would you reverse the bits of a number with log N arithmetic operations, where N is the number of bits in the integer (eg 32,64..) 15. Whats the simples way to check if the sum of two unsigned integers has resulted in an overflow. Solns: 2. Induction on i:1..n: Maintain the subarray with largest sum and suffix with largest sum and then update both after adding the i+1th element... 3. Sum of the numbers or copy i into A[i] so on till conflict. 4. Update deltaY while incrementing x. Have to multiply so that the deltay is not a floating pt number. 5. Find the largest 10**n less than given number, then div etc. 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 an 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 - -------------------- from csri ------------------------------- 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. 3. Write a function to reverse a singly linked list, given number of links to reverse. 4. Write a function to convert an int to a string. 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. Ans. Sibling and firstchild ptr. 9. 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]. eg. tr -abc -xyz to be and not to be <- input to ye xnd not to ye <- output 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? 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 parenthesesinserted where necessary. ----------------------------------------------------------------------------- There are 4 men 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 man walks at a different speed. A pair must walk together at the rate of the slower mans pace. Man 1:1 minute to cross Man 2: 2 minutes to cross Man 3: 5 minutes to cross Man 4: 10 minutes to cross For example if Man 1 and Man 4 walk across first. 10 Minutes have elapsed when they get to the other side of the bridge. If Man 4 returns with the flashlight. A total of 20 minutes have passed and you have failed the mission. See how quick you can solve this!