Technical Interview Questions For Computer Science Programmers
The following is a list of questions which have been floating around some
Internet circles. They are excellent prep questions for a technical interview.
I haven't made any attempt to clean them up, spelling or organization wise.
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.
Jeeve network sites: Easter Eggs | GoofUps | Lite Topics | Ask a Fool
AceTheInterview.com
Definitive source for technical Interviews
Need help with your next project?
Submit Q & A | Share your Experience | Tell a Friend | Contact Us
Where to Start
Résumé
Interview/Questions
• Interviews
• Common Questions
• Computer/Software
• General/Fundamentals
• Analytical
• Algorithms & Coding
• Language Specific
• C/C++
• Java
• Databases
• Internet Technoloy
• Misc.
• Microsoft Interview Q & A
• Question the Interviewer
After the Interview
Tips and References
Discussion Area
Search the Web.
Type it and go
Search AceTheInterview
Take our Survey
Be the first one to know
Join our mailing list to receive updates via e-mail when we add new Questions, Resumes or Cover Letters to this site.
( Max. 1 e-mail per week ).
Subscribe
Unsubscribe
Our top 10 contributors
1. sprihak (45)
2. deep (31)
3. amolh (20)
4. johny_bravo (18)
5. haha (17)
6. vikramjits (15)
7. raja (15)
8. johny1 (14)
9. rdakka (13)
10. Johnny Smartass (13)
*Updated daily.
General / Fundamentals
If a question hasn't been answered and you know the answer to, please try to take the time to answer it. If you don't know the answer to a question, check-out our community area. If you still can't find the answer, try asking in the community area or ask us.
--------------------------------------------------------------------------------
(Avg. of 285 ) : How do you multiply a variable by 16 without using the multiplication operator '*'?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 74 ) : What if you have to multiply by 15?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 65 ) : How can computer technology be integrated into 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 test this system?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 90 ) : How would you redesign an ATM?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 28 ) : Suppose we wanted to control different parts of a home using a Computer. What kind of software would you write to do this?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 26 ) : What is a balanced tree?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 16 ) : What is disk interleaving? Why do you need it?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 16 ) : What are various problems unique to distributed databases?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 12 ) : How would you decide what to test for given that there isn't enough time to test everything you want to.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 21 ) : Some general questions on Lex Yacc etc.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 15 ) : Fundamentals of RPC.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 7 ) : Tradeoff between time spent in testing a product and getting into the market first.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 9 ) : You're implementing the software for a IP router. When a packet comes in, the router has to decide which link to route the packet out on, based on it's destination IP address. Don't worry about changes in load - a packet destined for a given IP address will always go out the same link. How would you implement this? Optimized for speed? For space?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 30 ) : Find the fastest, simplest algorithm you can for determining if two rectangles overlap.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 13 ) : You're part of the QA team for a large web-site. You want to create as much automated testing as possible. What could/would you test? How? How much maintenance would these tests require as the web site changes?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 13 ) : What would be your language of choice for implementing CGI programs on a web server? Why?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 9 ) : How do you swap two integers without using any extra memory?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 4 ) : Describe the most interesting software project you've done in school.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 8 ) : What was the most difficult program you had to write?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 5 ) : What are the steps you take to write a program?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 8 ) : What is the difference between multitasking and multithreading and how does it work in vxWorks?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 7 ) : Name 7 layers of OSI models and define their functionality.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 13 ) : OSI layers and what devices work at each layer, examples of netowrk topology, when and why you would use each, pros and cons of each, etc.
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 6 ) : What layer of the OSI model does routers work on?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 9 ) : Explain inheritance
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 5 ) : What is a linked list
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 12 ) : How will you test vending machine?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent
| View Answers
--------------------------------------------------------------------------------
(Avg. of 14 ) : How would you go about learning a new programming language under high-pressure conditions?
Rate it:
Not useful at all
Ok.
Good
Very Good
Excellent