NYOJ--19--next_permutation（）--擅长排列的小明

/*Name: NYOJ--19--擅长排列的小明Author: shen_渊 Date: 20/04/17 11:06Description: 这道题可以DFS，然而用next_permutation更简单些主要是全排列，将所有字符串考虑到后，只输出前m个字符 */#include<bits/stdc++.h>#include<cstdlib>using namespace std;int arr[10] = {1,2,3,4,5,6,7,8,9};int main(){//freopen("in.txt","r",stdin);ios::sync_with_stdio(false);int N;cin>>N;while(N--){int n,m;cin>>n>>m;string str = "";for(int i=0;i<n;++i)str+='0'+arr[i];string str1,str2 = str.substr(0,m);cout<<str2<<endl;while(next_permutation(str.begin(),str.end())){if((str1 = str.substr(0,m))!= str2){str2 = str.substr(0,m);cout<<str2<<endl;}} }return 0;}