C / C++ / MFC

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

typedef void (*FOUND)(char*);

void PermRec(char *str, char *buf, FOUND callback)
{
  int i, n;
  char *buf2;
  if (*str == '\0')
  {
    (*callback)(buf);
    return;
  }
  n = strlen(buf);
  buf2 = malloc(n + 2);
  for (i = 0; i <= n; i++)
  {
    if (i != 0) memcpy(buf2, buf, i);
    buf2[i] = *str;
    if (i != n) memcpy(buf2 + i + 1, buf + i, n - i);
      PermRec(str + 1, buf2, callback);
  }
  free(buf2);
}

void EnumPermutations(char *str, FOUND callback)
{
  PermRec(str, "", callback);
}

void foundone(char *str)
{
  printf("%s\n", str);
}

int main (int argn, char **argv)
{
  if (argn <= 1)
  {
    printf ("Usage:\n  %s <string>\neg:\n  %s 123", argv[0], argv[0]);
    return 1;
  }
  EnumPermutations(argv[1], foundone);
}

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

void swap(char* pc1,char* pc2)
{
	char ch;
	ch = *pc1;
	*pc1 = *pc2;
	*pc2 = ch;
}

void perm (char* s,int pos)
{
	if (pos == (int)strlen(s))		
	{
		printf("%s\n",s);
		return;
	}

	for (int i=pos;i < (int)strlen(s);i++)
	{
		swap(s+pos,s+i);
		perm(s,pos+1);
		swap(s+pos,s+i);
	}

}


int main(int argc, char* argv[])
{
	char s[] = "abc";
	perm(s,0);
	return 0;
}