python/TangDou/LuoGuBook/P1157_dfs_vector.cpp

#include <bits/stdc++.h>

using namespace std;
int n, r;
//此答案，不吸氧，第8个测试点TLE，吸氧后通过。
void dfs(int step, vector<int> path, int m) {
    if (step == n + 1) return;
    if (m == r) {
        for (int i = 0; i < r; i++) printf("%3d", path[i]);
        printf("\n");
        return;
    }
    //下一个数字选择上
    vector<int> p1 = path;
    p1.push_back(step + 1);
    dfs(step + 1, p1, m + 1);

    //下一个数字放弃掉
    dfs(step + 1, path, m);
}

int main() {
    cin >> n >> r;
    dfs(0, {}, 0);
    return 0;
}