Data Structures FAQ

FREQUENTLY ASKED QUESTIONS

• ·         Write your own C program to implement the atoi() function
• ·         Implement the memmove() function. What is the difference between the memmove()                                                                                and memcpy() function?
• ·         Write C code to implement the strstr() (search for a substring) function.
• ·         Write your own printf() function in C
• ·         Implement the strcpy() function.
• ·         Implement the strcmp(str1, str2) function.
• ·         Implement the substr() function in C.
• ·         Write your own copy() function
• ·         Write C programs to implement the toupper() and the isupper() functions
• ·         Write a C program to implement your own strdup() function.
• ·         Write a C program to implement the strlen() function
• ·         Write your own strcat() function
• ·         Write a C program to swap two variables without using a temporary variable
• ·         What is the 8 queens problem? Write a C program to solve it.
• ·         Write a C program to print a square matrix helically.
• ·         Write a C program to reverse a string
• ·         Write a C program to reverse the words in a sentence in place.
• ·         Write a C program generate permutations.
• ·         Write a C program for calculating the factorial of a number
• ·         Write a C program to calculate pow(x,n)?
• ·         Write a C program which does wildcard pattern matching algorithm
• ·         How do you calculate the maximum subarray of a list of numbers?
• ·         How to generate fibonacci numbers? How to find out if a given number is a                                                                                        fibonacci number or not? Write C programs to do both.
• ·         Solve the Rat In A Maze problem using backtracking.
• ·         What Little-Endian and Big-Endian? How can I determine whether a machine's                                                                                   byte order is big-endian or little endian? How can we convert from one to another?
• ·         Write C code to solve the Tower of Hanoi problem.
• ·         Write C code to return a string from a function
• ·         Write a C program which produces its own source code as its output
• ·         Write a C progam to convert from decimal to any base (binary, hex, oct etc...)
• ·         Write C code to check if an integer is a power of 2 or not in a single line?
• ·         Write a C program to find the GCD of two numbers.
• ·         Finding a duplicated integer problem
• ·         Write code to remove duplicates in a sorted array.
• ·         Find the maximum of three integers using the ternary operator.
• ·         How do you initialize a pointer inside a function?
• ·         Write C code to dynamically allocate one, two and three dimensional arrays (using malloc())
• ·         How would you find the size of structure without using sizeof()?
• ·         Write a C program to multiply two matrices.
• ·         Write a C program to check for palindromes.
• ·         Write a C program to convert a decimal number into a binary number.
• ·         Write C code to implement the Binary Search algorithm.
• ·         Wite code to evaluate a polynomial.
• ·         Write code to add two polynomials
• ·         Write a program to add two long positive numbers (each represented by linked lists).
• ·         How do you compare floating point numbers?
• ·         What's a good way to implement complex numbers in C?
• ·         How can I display a percentage-done indication on the screen?
• ·         Write a program to check if a given year is a leap year or not?
• ·         Is there something we can do in C but not in C++?
• ·         How to swap the two nibbles in a byte ?
• ·         How to scan a string till we hit a new line using scanf()?
• ·         Write pseudocode to compare versions (like 115.10.1 vs 115.11.5).
• ·         How do you get the line numbers in C?
• ·         How to fast multiply a number by 7?
• ·         Write a simple piece of code to split a string at equal intervals
• ·         Is there a way to multiply matrices in lesser than o(n^3) time complexity?
• ·         How do you find out if a machine is 32 bit or 64 bit?
• ·         Write a program to have the output go two places at once (to the screen and to a file also)
• ·         Write code to round numbers
• ·         How can we sum the digits of a given number in single statement?
• ·         Given two strings A and B, how would you find out if the characters in B were a subset                                                                        of the characters in A?
• ·         Write a program to merge two arrays in sorted order, so that if an integer is in both the                                                                    arrays, it gets added into the final array only once. *
• ·         Write a program to check if the stack grows up or down
• ·         How to add two numbers without using the plus operator?
• ·         How to generate prime numbers? How to generate the next prime after a given prime?
• ·         Write a program to print numbers from 1 to 100 without using loops!
• ·         Write your own trim() or squeeze() function to remove the spaces from a string.
• ·         Write your own random number generator function in C.*
• ·         Write your own sqrt() function in C

Data Structures Part 6

Can you construct a tree using postorder and preorder traversal? 

          

No Consider 2 trees below Tree1 a b Tree 2 a b preorder = ab postorder = ba Preorder and postorder do not uniquely define a binary tree. Nor do preorder and level order (same example). Given an expression tree, evaluate the expression and obtain a paranthesized form  of the expression.  The code below prints the paranthesized form of a tree. infix_exp(p) { if(p) { printf("("); infix_exp(p->left); printf(p->data); infix_exp(p->right); printf(")"); } } What is a threaded binary tree?   Since traversing the three is the most frequent operation, a method  must be devised to improve the speed. This is where Threaded tree comes into picture. If the right link of a node in a tree is NULL, it can be replaced by the address of its inorder successor. An extra field called the rthread is used.  If rthread is equal to 1, then it means that the right link of  the node points to the inorder success. If its equal to 0, then the right link represents an link connecting the right subtree. struct node { int value; struct node *left; struct node *right; int rthread; } Function to find the inorder successor mynode *inorder_successor(mynode *x) { mynode *temp; temp = x->right; if(x->rthread==1)return(temp); while(temp->left!=NULL)temp = temp->left; return(temp); } Function to traverse the threaded tree in inorder void inorder(mynode *head) { mynode *temp; if(head->left==head) { printf("\nTree is empty!\n"); return; } temp = head; for(;;) { temp = inorder_successor(temp); if(temp==head)return; printf("%d ", temp->value); } } Inserting toward the left of a node in a threaded binary tree. void insert(int item, mynode *x) { mynode *temp; temp = getnode(); temp->value = item; x->left = temp; temp->left=NULL; temp->right=x; temp->rthread=1; } Function to insert towards the right of a node in a  threaded binary tree. void insert_right(int item, mynode *x) { mynode *temp, r; temp=getnode(); temp->info=item; r=x->right; x->right=temp; x->rthread=0; temp->left=NULL; temp->right=r; temp->rthread=1; } Function to find the inorder predecessor (for a left threaded binary three) mynode *inorder_predecessor(mynode *x) { mynode *temp; temp = x->left; if(x->lthread==1)return(temp); while(temp->right!=NULL) temp=temp->right; return(temp); }

Data Structures Part 5

How do you convert a tree into an array? 

          

The conversion is based on these rules If i > 1, i/2 is the parent If 2*i > n, then there is no left child, else 2*i is the left child. If (2*i + 1) > n, then there is no right child, else (2*i + 1) is the  right child. Converting a tree to an array is very easy Suppose we have a tree like this A B C D E F G The array representation would be a[1] a[2] a[3] a[4] a[5] a[6] a[7] A B C D E F G That is, for every node at position i in the array, its left child  will be stored at position (2*i) and right child at (2*i + 1). The root starts at position 1. A full N-ary tree has M non-leaf nodes, how many leaf nodes does it have?  Use Geometric progression. M + (N ^ (n-1)) = (1 - (N ^ n)) / (1 - N) Here (N ^ (n-1)) is the number of leaf-nodes. Solving for this leads to the answer Leaf nodes = M * (N - 1) + 1 Suppose you have a 3-ary tree A B C D E F G H I J K L M So, here M=4 and N=3. So using the formula above, Leaf nodes = M * (N - 1) + 1 = 4 * (3 - 1) + 1 = 9