Thread: Recurssion issues.

Hi. I've posted here regarding this before, but I moved on and am coming back to it now since I am still having trouble figuring the string permutation using recursion issue.

The issue I am having is that somewhere before checkpoint 2 there is a segmentation fault. My program just keeps spitting out the same 2 permutations until until it gives the error message. I would love to understand why?

Code:

$ ./test.1 -o test.1.c | sort -u
chechpoit-1: ABCD
chechpoit-1: CBAD
checkpoint-2 ABCD
checkpoint-2 CBAD

Code:

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

void swap(char *a, char *b){
char temp;

temp = *a;
*a = *b;
*b = temp;
}




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

 if (i == strlen(str))
     printf("%s\n", str);
 else{

      for( j = i; j <= strlen(str); j++){
printf("chechpoit-1: %s\n", str);
fflush(0);
      swap(str+i,str+n);
printf("checkpoint-2 %s\n", str);
      permute(str, i, n);
printf("checkpoint-3 %s\n", str);
      swap(str+i,str+n);}
}
}

int main(void){


char *ptr; 
char string[] = "ABCD";

ptr = string;

permute(ptr,0,2);
return 0;}