Finding all possible permutation of a string

Tags:

algorithm

I have the following program for finding all possible permutations of a string.

``````#include <stdio.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 i, int n)
{
int j;
if (i == n)
printf("%s\n", a);
else
{
for (j = i; j <= n; j++)
{
swap((a+i), (a+j));
permute(a, i+1, n);
swap((a+i), (a+j)); //backtrack
}
}
}

/* Driver program to test above functions */
int main()
{
char a[] = "abcd";
permute(a, 0, 3);
getchar();
return 0;
}
``````

I need to know is there any better way(efficient) to find all permutations because this algorithm is having O(n^n) efficiency.

Thank you.. :-)

532

Gokul

It is there in standard

``````#include<algorithm>
std::vector<int> vec;
std::next_permutation(std::begin(vec), std::end(vec));
``````

In case of string

``````# include<string>
#include<algorithm>

std::string str ="abcd"
do{
std::cout<<str<<"\n";

} while(std::next_permutation(std::begin(str), std::end(str)));
``````
193