word combination / string combination

#include<stdio.h>
#include<string.h>
#define MAX 100


void swap(char* src, char* dst)
{
    char ch = *dst;
    *dst = *src;
    *src = ch;
}

int permute(char *set, int begin, int end)
{

    int i;
    int range = end - begin;

    if (range == 1)
    {
        printf("%s\n", set);
    }

    else

    {
        for (i = 0; i < range; i++)
        {

            swap(&set[begin], &set[begin + i]);

            permute(set, begin + 1, end);

            swap(&set[begin], &set[begin + i]); /*set back*/

        }
    }
}

void main()
{
    char str[MAX];

    printf("Enter the string: ");

    /*as ussual warnings with gets*/
    gets(str);
    permute(str, 0, strlen(str));

}