深搜板子加一点点修改，适合初学者体会深搜，具体看代码
题目链接

ACcode

#include<bits/stdc++.h>using namespace std;int a, b;bitset<50>vis;//剪枝
int d[50];void dfs(int x) {if (x == b + 1) {for (int i = 1;i <= b;i++)cout << setw(3) << d[i];cout << '\n';return;}for (int i = x;i <= a;i++) {if (vis[i])continue;if (d[x - 1] > i)continue;//题目要求必须从小到大输出vis[i] = 1;d[x] = i;dfs(x + 1);vis[i] = 0;d[x] = 0;}
}int main()
{ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);cin >> a >> b;dfs(1);return 0;
}