暴力枚举 洛谷1157

#include
using namespace std;
int a[22];
int main()
{
	int n, r;
	cin >> n >> r;
	for (int S = (1 << n) - 1; S >= 0; S--)
	{
		int cnt = 0;
		for (int i = 0; i < n; ++i)
		{
			if (S&(1 << i))
				a[cnt++] = i;
		}
		if (cnt == r)
		{
			for (int i = r - 1; i >= 0; --i)
				printf("%3d", n - a[i]);//用高位表示1，所以需要反过来输出
			cout << endl;
		}
	}
	return 0;
}