Acwing93: https://www.acwing.com/problem/content/95/

https://www.acwing.com/problem/content/95/

这一题输出要求升序，vecotr<vector<int,int>>sort居然可以将里层的vector排序，amazing~

Code：

#include<bits/stdc++.h>
using namespace std;

#define PII pair<int, int>
#define x first
#define y second
const int inf = 0x3f3f3f3f;
#define int long long
const int N = 30;
int n, m;

vector<vector<int>> ans;
void sol() {
	cin >> n >> m;
	for (int i=0; i< 1<<n; i++){
		int k = 0;
		for (int j=0; j<n; j++){
			if(i >> j & 1) k++;
		}
		if(k!=m) continue;
		vector<int> v;
		for (int j=0; j<n; j++){
			if(i >> j & 1) v.push_back(j+1);
		}
		ans.push_back(v);
	}
	sort(ans.begin(), ans.end());
	for (auto v : ans){
		for (auto u : v){
			cout << u << ' ';
		}
		cout << '\n';
	}
}

signed main(){
	// ios::sync_with_stdio(false);
	// cin.tie(nullptr);

	int T_T=1;
	// cin >> T_T;
	while (T_T--) sol();

	return 0;
}