In this c programming tutorial we are going to see a c program to print all permutations of a given string. Now let’s see what is a permutation.

A permutation, also called an arrangement number or order, is a rearrangement of the elements of an ordered list S into a one-to-one correspondence with S itself. A string of length n has n! permutation.Source: Mathword

Below are the permutations of string CBA.

ABC, ACB, BAC, BCA, CAB, CBA

**Algorithm Paradigm:** Backtracking

**Time Complexity:** O(n*n!)

Please write comments if you find the above codes/algorithms incorrect, or find other ways to solve the same problem.

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#include <stdio.h> #include <string.h> /* Function to swap values at two pointers */ void swap(char *x, char *y) { char temp; temp = *x; *x = *y; *y = temp; } /* Function to print permutations of string This function takes three parameters: 1. String 2. Starting index of the string 3. Ending index of the string. */ void permute(char *a, int l, int r) { int i; if (l == r) printf("%s\n", a); else { for (i = l; i <= r; i++) { swap((a+l), (a+i)); permute(a, l+1, r); swap((a+l), (a+i)); //backtrack } } } /* Driver program to test above functions */ int main() { char str[] = "SHRI"; int n = strlen(str); permute(str, 0, n-1); return 0; } |