Leetcode 39 combinations of sum (backtracking algorithm solving)

Subject description:

Given a non-repeating array element candidates and a target number target, you can find all the candidates for the target numbers and combinations thereof.

Digital candidates may be selected without limitation repeated

Source: stay button (LeetCode)
link: https: //leetcode-cn.com/problems/combination-sum

class Solution {
private:
    vector<vector <int>> results;
    vector<int> solution;
public:
    void backtracking(vector<int> candidates, int target, int start){
        if(target < 0)
            return;
        if(target == 0){
            results.push_back(solution);
            return;
        }
        for(int i=start; i<candidates.size() && candidates[i]-target<=0; i++){
            solution.push_back(candidates[i]);
            backtracking(candidates, target-candidates[i], i);
            solution.pop_back();
        }
    }
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        std::sort(candidates.begin(), candidates.end());
        backtracking(candidates, target, 0);
        return results;        
    }
};

DFS depth-first search algorithm

vector: 　1. push_back()

　　　　  2. pop_back()