permutations and combinations [closed]

Use the Exeter algorithm

#include <stdio.h>
#include <string.h>

void swap(char *x, char *y){
    char w;
    w = *x;
    *x = *y;
    *y = w;
}

void permute(char *str, int start, int n){
    int i;

    if(start == n-1)
        printf("%s\n", str);
    else
        for(i = start; i < n; i++){
            swap(str+i, str+start);
            permute(str, start+1, n);
            swap(str+i, str+start);
        }
}

int main(){

    char line[10], str[10];
    int n, op;

    printf("Enter a string: ");
    if( fgets(line, 10, stdin) == NULL ){
        printf("Ops! Early stop\n");
        return 1;
    }


    if( sscanf(line, "%s", str) != 1 ){
        printf("Next time put some valid characters\n");
        return 1;
    }

    n = strlen(str);
    permute(str, 0, n);
    return 0;
}

Note: This algorithm generates all the possibles permutations