程序代码：

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

#define SWAP(x, y, t) ((t) = (x), (x) = (y), (y) = (t))

void foo(char* s, int from, int to);

int main(void) {
    char num[5];
    scanf("%5s", num);
    foo(num, 0, strlen(num) - 1);
    putchar('\n');
    return 0;
}

void foo(char *s, int from, int to) {
    int i, j, t;

    if(to <= 1) return;

    if(from == to) {
        for(i = 0; i <= to; i++) putchar(s[i]);

        putchar('\t');

    } else {
        for(j = from; j <= to; j++) {
            SWAP(s[j], s[from], t);
            foo(s, from + 1, to);
            SWAP(s[j], s[from], t);
        }
    }
}