利用二进制枚举解决问题

#include <iostream>
using namespace std;

int a[20]={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};

int main(){
	int n;
	cin >> n;
	for(int op=0;op< 1<<n ;op++){
		for(int i=0;i<n;i++){
			if(op >> i & 1 ){
				cout << a[i] << " ";
			}
		}
		cout << endl;
	}
}