recursivePermutation.c

recursivePermutation.c

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


void swap(char* x, char* y );
void permute(char* str, unsigned int l, unsigned int s);

int main()
{
    char str[] = "ABCDA";
    unsigned int n = strlen(str);
    
    permute(str, 1, n-2); 
    
    getchar();
    return 0;
}

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

void permute(char* str, unsigned int l, unsigned int s)
{
   int i;
   if (l == s)
     printf("%s\n", str);
   else
   {
       for (i = l; i <= s; i++)
       {
          swap((str+l), (str+i));
          permute(str, l+1, s);
          swap((str+l), (str+i)); //backtrack
       }
   }
}