String character permutation.

 
/* 
 * File:   heap.c
 * Author: cassius
 *
 * Created on 19 de Novembro de 2006, 22:27
 */

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



static void print_recursive(char* str, int pos, int length)
{
    int k;
    char first, current;
    
    if(pos >= (length-1) )
        fprintf(stdout, "%s ", str);
    else 
    {
        first = str[pos];
    
        for(k = pos; k < length; k++) 
        {
            /* swap chars */
            current = str[k];
            str[pos] = current;
            str[k] = first;
        
            print_recursive(str, pos + 1, length);
            /* swap it back. */
            str[k] = current;
        }
        str[pos] = first;
    }
}

void print(char* str) 
{
    int len = strlen(str);
    
    print_recursive(str, 0, len);
    fprintf(stdout, ".\n");
}


/*
 * 
 */
int
main(int argc, char** argv) {
    char max_str[100];
    fprintf(stdout, "Please, digite a word.\n");
    
    fscanf(stdin, "%s ", max_str);
    
    print(max_str);
    fprintf(stdout, "Exiting ...");
    
    return (EXIT_SUCCESS);
}