leetcode. 39 --- combined sum

Combinatorial summation

Answer key ：

The code is as follows ：

class Solution {
    
public:
    vector<vector<int>> ans;
    vector<int> path;
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
    
        dfs(candidates,0,target);
        return ans;
    }
    void dfs(vector<int>&a,int u,int target)
    {
    
        if(target < 0) return; // dissatisfaction 
        if(target == 0){
      // The scheme is legal , It was recorded that path in 
            ans.push_back(path);
            return;
        }
        for(int i = u;i < a.size();i++)
        {
    
            if(a[i] <= target){
    
                path.push_back(a[i]);
                dfs(a,i,target - a[i]); // use target - a[i] To calculate , Reduced to 0 Can 
                path.pop_back(); // recovery 
            }
        }
    }
};