leetcode-77-combinations

class Solution {
public:
    vector<vector<int>> combine(int n, int k) {
        vector<vector<int>> res;
        vector<int> tmp;
        dfs(res, tmp, 1, k, n);
        return res;
    }
	
    
    void (vector<vector<int>> &res, vector<int> tmp, int start, int k, int n){
        if(tmp.size() == k) {
            res.push_back(tmp);//与java不同，不需要新建vector对象。
            return; 
        }
        for(int i = start; i <= n; i++){
            tmp.push_back(i);
            combine_func(res,tmp, i + 1, k, n);
            tmp.pop_back();
        }
    }
};