77. 组合(dfs)(LeetCode)

77. 组合

class Solution {
public:

    vector<vector<int>> ans;
    vector<int> path;

    vector<vector<int>> combine(int n, int k) {
        dfs(n, k, 1);
        return ans;    
    }

    void dfs(int n, int k, int st){
        if(!k){
            ans.push_back(path);
            return;
        }
        for(int i = st; i <= n; ++i){
            path.push_back(i);
            dfs(n, k - 1, i + 1);
            path.pop_back();
        }
    }
};