【LeetCode 53】39.组合总和

class Solution {
private:
    vector<vector<int>>result;
    vector<int> path;
    void backtracking(vector<int>&candidates,int target,int sum,int startIndex)
    {
        if(sum>target)
        {
            return;
        }
        if(sum==target)
        {
            result.push_back(path);
            return;
        }
        
          for (int i = startIndex; i < candidates.size(); i++)
         //剪枝操作
        //for(int i=startIndex;i<candidates.size()&&sum+candidates[i]<=target;i++)
        {
            /* code */
            sum+=candidates[i];
            path.push_back(candidates[i]);
            //不需要i+1表示可以重复读取当前的数
            backtracking(candidates,target,sum,i);
            sum-=candidates[i];
            path.pop_back();
        }
        
    }
public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        result.clear();
        path.clear();
        backtracking(candidates,target,0,0);
        return result;
    }
};