http://www.lightoj.com/volume_showproblem.php?problem=1023

题意：26字母全排列

思路：用next_permutation或者思维想一下都可以

/** @Date    : 2016-12-17-13.28

  * @Author  : Lweleth (SoungEarlf@gmail.com)

  * @Link    : https://github.com/

  * @Version :

  */

#include<bits/stdc++.h>

#define LL long long

#define PII pair

#define MP(x, y) make_pair((x),(y))

#define fi first

#define se second

#define PB(x) push_back((x))

#define MMG(x) memset((x), -1,sizeof(x))

#define MMF(x) memset((x),0,sizeof(x))

#define MMI(x) memset((x), INF, sizeof(x))

using namespace std;

const int INF = 0x3f3f3f3f;

const int N = 1e5+20;

const double eps = 1e-8;

int main()

{

    int T;

    int cnt = 0;

    cin >> T;

    string s = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    while(T--)

    {

        int n, m;

        cin >> n >> m;

        string t = s;

        int ct = 0;

        printf("Case %d:\n", ++cnt);

        while(ct < m)

        {

            for(int i = 0; i < n; i++)

                printf("%c", t[i]);

            printf("\n");

            ct++;

            next_permutation(t.begin(), t.begin() + n);

            if(t == s)

                break;

        }

    }

    return 0;

}