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### Common Interview Questions

Common Interview Questions

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.
4.       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.
5.       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.
6.       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.
7.       A version of the "There are three persons X Y Z, one of which always lies"..
8.       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.
9.       If you are on a boat and you throw out a suitcase, Will the level of water increase.
10.   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.
a.       Man 1:1 minute to cross
b.      Man 2: 2 minutes to cross
c.       Man 3: 5 minutes to cross
d.      Man 4: 10 minutes to cross
11.   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?
12.   One train leaves Los Angeles at 15 MPH 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?
13.   Imagine that you have 26 constants, labelled A through Z. Each constant is assigned a value in the following way: A = 1; the rest of the values equal their position in the alphabet (B corresponds to the second position so it equals 2, C = 3, etc.) raised to the power of the preceeding constant value. So, B = 2 ^ (A's value), or B = 2^1 = 2. C = 3^2 = 9. D = 4^9, etc., etc. Find the exact numerical value to the following equation:
(X - A) * (X - B) * (X - C) * ... * (X - Y) * (X - Z)
14.   You have 12 balls. All of them are identical except one, which is either heavier or lighter than the rest - it is either hollow while the rest are solid, or solid while the rest are hollow. You have a simple two-armed scale, and are permitted three weighings. Can you identify the odd ball, and determine whether it is hollow or solid.
Programming questions that require thinking
1.       Write a routine to draw a circle (x ** 2 + y ** 2 = r ** 2) without making use of any floating point computations at all.
2.       Given only putchar (no sprintf, itoa, etc.) write a routine putlong that prints out an unsigned long in decimal.
3.       Give a one-line C expression to test whether a number is a power of 2. [No loops allowed - it's a simple test.]
4.       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).
5.       What are the different ways to say, the value of x can be either a 0 or a 1.
6.       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.
7.       Give a fast way to multiply a number by 7.
8.       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.
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.
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?
Given an expression tree with no parentheses in it, write the program to give equivalent infix expression with parentheses inserted where necessary.
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.
Give me an algorithm and C code to find the subarray with the largest sum given an array containing both positive and negative integers.
Write a function that returns the factorial of a number.
Write a function that computes the nth number in the Fibonacci sequence.
Write an implementation of strlen().
Switch the integer values stored in two registers without using any additional memory.
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.
Write a small lexical analyzer - interviewer gave tokens. expressions like "a*b" etc.
Write a routine that prints out a 2-D array in spiral order!
Write code for reversing a linked list.
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).
Microsoft question

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 ?
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.
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 ].
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 ].
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 ].
Give a one-line C expression to test whether a number is a power of 2. [No loops allowed - it's a simple test.]
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.
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.
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).
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
(a-1) xor a == 0 - What does this do?
How can you print singly linked list in reverse order? (it's a huge list and you cant use recursion)
How can you find out if there is a loop in a very long list?
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)
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..)
Whats the simples way to check if the sum of two unsigned integers has resulted in an overflow.
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...
Sum of the numbers or copy i into A[i] so on till conflict.
Update deltaY while incrementing x. Have to multiply so that the deltay is not a floating pt number.
Find the largest 10**n less than given number, then div etc.
Infinite.
Shivku said this question is garbled thru ages.
reverse the pointers till you reach the end and print-and-reverse as you return.
Have two 'threads' one at twice the speed of the other traversing the list and see if at anytime they meet.
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.
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.
if (a+b) < a or (a+b) < b then overflow has occurred
Data structures and algorithms questions

Write a function and the node data structure to visit all of the nodes in a binary tree.
You know what a queue is .... Implement a queue class with Java. What is the cost of enqueue and dequeue? Can you improve this? What if the queue is full (I was using an looping array)? What kind of mechanism would you use to increase its size?
Give an algorithm that calculates the distance between two text strings (only operations you can have are: delete, add, and change, one by one).
Given the definition of a sequence (5 4 7 6 is, but 1 2 4 5 is not), write an algorithm to check if an arbitrary array is a sequence or not. Once I figured out a solution, I was asked to do a space and time complexity analysis.
Describe a situation where concurrent access would lead to inconsistency in your application. How would you solve this problem?
You are given a list of n numbers from 1 to n-1, with one of the numbers repeated. Devise a method to determine which number is repeated.
Write an algorithm to detect loop in a linked list.
Given the time, devise an algorithm to calculate the angle between the hour and minute hands of an analog clock.
Devise an algorithm for detecting whether a given string is a palindrome (spelled the same way forwards and backwards). For example, "A man, a plan, a canal, Panama."
Given an eight-bit bitmap graphics file, devise an algorithm to convert the file into a two-bit ASCII approximation.
Insert in a sorted list
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).
Delete an element from a doubly linked list.
Write a function to find the depth of a binary tree.
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.
Besides communication cost, what is the other source of inefficiency in RPC?
Ways of optimizing symbol table storage in compilers.
A walk-through through the symbol table functions, lookup() implementation etc - The interv. was on the Microsoft C team.
Given an array t[100] which contains numbers between 1..99. Return the duplicated value. Try both O(n) and O(n-square).
Given an array of characters. How would you reverse it. ? How would you reverse it without using indexing in the array.
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)
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.
Do a breadth first traversal of a tree.
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).
What is a balanced tree
How would you find a cycle in a linked list? Try to do it in O(n) time. Try it using a constant amount of memory.
Implement an algorithm to reverse a doubly linked list.
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.
The Web can be modeled as a directed graph. Come up with a graph traversal algorithm. Make the algorithm non-recursive and breadth-first.
How would you implement a hash table ? How do you deal with collisions?
How would you find a cycle in a linked list? Try to do it in O(n) time. Try it using a constant amount of memory.
Given a history of URLs, how would you determine if a particular URL had been seen before?
Since pages can have multiple URLs pointing to them, how can you make sure you've never seen the same CONTENT before?
Write a function to print all of the permutations of a string.
Come up with the plan on how to traverse a graph, as well as to quickly determine if a given URL is one of the million or so you've previously seen.
The Web can be modeled as a directed graph. Come up with a graph traversal algorithm. Make the algorithm non-recursive and breadth-first.
Implement an algorithm to reverse a singly linked list. (with and without recursion)
Implement an algorithm to reverse a doubly linked list.
Implement an algorithm to insert in a sorted list.
Delete an element from a doubly linked list.
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.
Implement an algorithm to sort an array.
Given a sequence of characters, how will you convert the lower case characters to upper case characters?
Write a routine that prints out a 2-D array in spiral order.
Count the number of set bits in a number without using a loop.
Give me an algorithm and C code to shuffle a deck of cards, given that the cards are stored in an array of ints. Try to come up with a solution that does not require any extra space.
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.
How would you print out the data in a binary tree, level by level, starting at the top?
Given an array of characters which form a sentence of words, give an efficient algorithm to reverse the order of the words in it.
Write a function to find the depth of a binary tree.
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).
How would you implement a queue from a stack?
Write a funtion that finds repeating characters in a string.
Write a routine to reverse a series of numbers without using an array.
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)
From CSRI

Write a function to check if two rectangles defined as below overlap or not.
struct rect {
int top, bot, left, right;
} r1, r2;
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.
Write a function to reverse a singly linked list, given number of links to reverse.
Write a function to convert an int to a string.
Some weird problem on vector calculus with some transformation matrices being applied - need paper and pencil to describe it.
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?
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.
How do you represent an n-ary tree? Write a program to print the nodes of such a tree in breadth first order.
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="" p="">
to ye xnd not to ye   <- output="" p="">
C syntax, semantics and simple programming questions

What does the term cast refer to? Why is it used?
In arithmetic expressions, to what data type will the C compiler promote a character?
What is the difference between a statement and a block?
Increment the variable next three different ways.
How is a comment formed in C.
From the standpoint of programming logic, what is the difference between a loop with the test at the top, and a loop where the test is at the bottom?
Specify the skeletons of two C loops with the test at the top.
Specify a C loop with the test at the bottom.
What is the switch statement?
What does a break statement do? Which control structures use it?
In a loop, what is the difference between a break and continue statement?
Where may variables be defined in C?
What is the difference between a variable definition and a variable declaration?
What is the purpose of a function prototype?
What is type checking?
To what does the term storage class refer?
List C's storage classes and what they signify.
State the syntax for the printf() and scanf() functions. State their one crucial difference with respect to their parameters.
With respect to function parameter passing, what is the difference between call-by-value and call-by-reference? Which method does C use?
What is a structure and a union in C?
Define a structure for a simple name/address record.
What does the typedef keyword do?
Use typedef to make a short-cut way to declare a pointer to the nameAddr structure above. Call it addrPtr.
Assuming the variable address above, how would one refer to the city portion of the record within a C expression?
What is the difference between: #include and #include "stdio.h"
What is #ifdef used for?
How do you define a constant in C?
Why can't you nest structure definitions?
Can you nest function definitions?
What is a forward reference?
What are the following and how do they differ: int, long, float and double?
Define a macro called SQR which squares a number.
Is it possible to take the square-root of a number in C. Is there a square-root operator in C?
Using fprintf() print a single floating point number right-justified in a field of 20 spaces, no leading zeros, and 4 decimal places. The destination should be stderr and the variable is called num.
What is the difference between the & and && operators and the | and || operators?
What is the difference between the -> and . operators?
What is the symbol for the modulus operator?
From the standpoint of logic, what is the difference between the fragment:
if (next < max)
next++;
else
next = 0;
and the fragment:
next += (next < max)? (1):(-next);
What does the following fragment do?
while((d=c=getch(),d)!=EOF&&(c!='\t'&&c!=' '&&c!='\b')) *buff++ = ++c;
Is C case sensitive (ie: does C differentiate between upper and lower case letters)?
Specify how a filestream called inFile should be opened for random reading and writing. the file's name is in fileName.
What does fopen() return if successful. If unsuccessful?
What is the void data type? What is a void pointer?
Declare a pointer called fnc which points to a function that returns an unsigned long.
Declare a pointer called pfnc which points to a function that returns a pointer to a structure of type nameAddr.
It is possible for a function to return a character, an integer, and a floating point number. Is it possible for a function to return a structure? Another function?
What is the difference between an lvalue and an rvalue?
Given the decimal number 27, how would one express it as a hexadecimal number in C?
What is malloc()?
What is the difference between malloc() and calloc()?
What kind of problems was C designed to solve?
write C code for deleting an element from a linked listy traversing a linked list efficient way of elimiating duplicates from an array
Declare a void pointer
Make the pointer aligned to a 4 byte boundary in a efficient manner
What is a far pointer (in DOS)
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.
Write C code to implement strtok() 'c' library function.
Implement strstr(), strcpy(), strtok() etc
Reverse a string.
Given a linked list which is sorted, how will you insert in sorted way.
Write a function that allocates memory for a two-dimensional array of given size (parameter x & y)
Write source code for printHex(int i) in C/C++
Write a function that finds the last instance of a character in a string.
C++ syntax, semantics and concepts questions

What is an object in C++?
What is a message?
What is a class?
What is an instance?
What is a super-class?
What is inheritance?
To what does message protocol refer?
What is polymorphism?
What are instance variables?
What are class variables?
What is a method?
In C++ what is a constructor? A destructor?
Compare and contrast C and C++.
What is cin and cout?
Contrast procedural and object oriented programming.
How do you link a C++ program to C functions?
Explain the scope resolution operator.
What are the differences between a C++ struct and C++ class?
How many ways are there to initialize an int with a constant?
How does throwing and catching exceptions differ from using setjmp and longjmp?
What is your reaction to this line of code?
delete this;
What is a default constructor?
What is a conversion constructor?
What is the difference between a copy constructor and an overloaded assignment operator?
When should you use multiple inheritance?
What is a virtual destructor?
Explain the ISA and HASA class relationships. How would you implement each in a class design?
When is a template a better solution than a base class?
What is the result of compiling this program in a C compiler? in a C++ compiler?
int __ = 0;
main() {
int ___ = 2;
printf("%d\n", ___ + __);
}
What is the difference between C and C++ ? Would you prefer to use one over the other ?
What are the access privileges in C++ ? What is the default access level ?
What is data encapsulation ?
What is inheritance ?
What is multiple inheritance ? What are it's advantages and disadvantages ?
What is polymorphism?
What do the keyword static and const signify ?
How is memory allocated/deallocated in C ? How about C++ ?
What is UML ?
What is the difference between a shallow copy and a deep copy ?
What are the differences between new and malloc?
What is the difference between delete and delete[]?
What are the differences between a struct in C and in C++?
What is the difference between a pointer and a reference?
When would you use a pointer? A reference?
What does it mean to take the address of a reference?
What does it mean to declare a function or variable as static?
What is the order of initalization for data?
What is name mangling/name decoration?
What kind of problems does name mangling cause?
How do you work around them?
What is a class?
What are the differences between a struct and a class in C++?
What is the difference between public, private, and protected access?
For class CFoo { }; what default methods will the compiler generate for you>?
How can you force the compiler to not generate them?
What is the purpose of a constructor? Destructor?
What is a constructor initializer list?
When must you use a constructor initializer list?
What is a: Constructor? Destructor? Default constructor? Copy constructor? Conversion constructor?
What does it mean to declare a... member function as virtual? member function as static? member varible as static? destructor as static?
Can you explain the term "resource acqusition is initialization?"
What is a "pure virtual" member function?
What is the difference between public, private, and protected inheritance?
What is virtual inheritance?
What is placement new?
What is the difference between operator new and the new operator?
What is exception handling?
Explain what happens when an exception is thrown in C++.
What happens if an exception is not caught?
What happens if an exception is throws from an object's constructor?
What happens if an exception is throws from an object's destructor?
What are the costs and benefits of using exceptions?
When would you choose to return an error code rather than throw an exception?
What is a template?
What is partial specialization or template specialization?
How can you force instantiation of a template?
What is an iterator?
What is an algorithm (in terms of the STL/C++ standard library)?
What is std::auto_ptr?
What is wrong with this statement? std::auto_ptr ptr(new char[10]);
It is possible to build a C++ compiler on top of a C compiler. How would you do this?

### A real life problem - Interview Question

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.

Put ur  code in any language as a comment !!

### Hibernate Interview Question - Difference between Merge and Update Method

One of the most frequently asked Hibernate Interview Question is "What is the difference between Merge and SaveOrUpdate methods"

Recently, One of the reader of this blog asked this question and i felt i should answer this question in detail.

When Save or SaveOrUpdate method is called on a detached object, it will throw NonUniqueObjectException with message "a different object with the same identifier value was already associated with the session." While Merge will convert Detached object to Persistent state and merge its contents.

Another Important Hibernate Interview question is "Difference between Load and Get method."

### Captcha generation Code in Java

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29``` ```import java.util.Random; public class Captcha { public String generateCaptcha() { Random random = new Random(); int length = 5; StringBuffer captchaStringBuffer = new StringBuffer(); for (int i = 0; i < length; i++) { int captchaNumber = Math.abs(random.nextInt()) % 60; int charNumber = 0; if (captchaNumber < 26) { charNumber = 65 + captchaNumber; } else if (captchaNumber < 52) { charNumber = 97 + (captchaNumber - 26); } else { charNumber = 48 + (captchaNumber - 52); } captchaStringBuffer.append((char) charNumber); } return captchaStringBuffer.toString(); } public static void main(String[] args) { Captcha captcha = new Captcha(); String str = captcha.generateCaptcha(); System.out.println(str); } } ```