C++ 代码

#include <iostream>
#include <vector>
using namespace std;
int n, m;
vector<int> ret;

void dfs(int idx){
    if(ret.size() + n - idx + 1 < m) return; //无法选m个就提前结束
    if(idx == n + 1 && ret.size() < m) return; 
    if(ret.size() == m){
        for(auto x : ret)
            cout << x << " ";
        cout << endl;
        return;
    }
    ret.push_back(idx);
    dfs(idx + 1);      //此数选取
    ret.pop_back();
    dfs(idx + 1);      //此数不选取
}

int main()
{
    cin >> n >> m;
    dfs(1);
    return 0;
}