北京大学机试 全排列 Easy *第一次见全排列，递归可破

#include<iostream>
#include<vector>
#include<string>
using namespace std;

bool vis[26];

void charge(string s,int cnt) {
	if (cnt == 0) {
		cout << s << endl;
		return;
	}
	for (int i = 0; i < 26; i++) {
		if (vis[i]) {
			vis[i] = false;
			//选中；
			charge(s + char(‘a‘ + i), cnt - 1);
			vis[i] = true;
		}
	}
}

int main() {
	string s;
	while (cin >> s) {
		fill(vis, vis + 26, false);
		for (int i = 0; i < s.size(); i++)
			vis[s[i] - ‘a‘] = true;
		charge("", s.size());
		cout << endl;
	}
}