# RANDOMIZED ALGORITHMS 3

QUESTION

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.\nSource: Mathword(http://mathworld.wolfram.com/Permutation.html)\n\nBelow are the permutations of string ABC.\nABC ACB BAC BCA CBA CAB.

``````#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;// = "ABC";
scanf("%s",str);
int n = strlen(str);
permute(str, 0, n-1);
return 0;
}`````` #### Ads Blocker Detected!!!

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