hutc-Permutation with Repetition参考代码

#include <stdio.h>
#include <algorithm>
using namespace std;
int ans;
int ok(char str[], int a, int b)
{
    if(b > a)
        for(int i = a; i < b; i++)
            if(str[i] == str[b])
                return 0;
    return 1;
}
void perm(char str[], int k, int m)
{
    int i;
    if(k == m)
    {
        ans++;
        for(i = 0; i <= m; i++)
            printf("%c", str[i]);
        printf("\n");
    }
    else
    {
        for(i = k; i <= m; i++)
            if(ok(str, k, i))
            {
                swap(str[k], str[i]);
                perm(str, k + 1, m);
                swap(str[k], str[i]);