leetcode 113. Path sum II medium

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leetcode  113. Path sum II    Medium          

Subject description:

Given a binary tree and a target and to find the sum of all paths from the root node of the leaf node is equal to a given target and path.

Description:  leaf node is a node has no child nodes.

Problem-solving ideas:

dfs

Code:

class Solution {
public:
    vector<vector<int>> pathSum(TreeNode* root, int sum) {
        if(root==nullptr)
            return {};
        
        vector<vector<int>> res;
        vector<int> out;
        dfs(root,0,sum,res,out);
        return res;
    }
    
    
    void dfs(TreeNode *root, int cur,int target,vector<vector<int>> &res,vector<int> &out){
        if(root==nullptr)
            return;
        
        cur += root->val;
        out.push_back(root->val);
        if(!root->left && !root->right && cur==target){
            res.push_back(out);
        }
        
        dfs(root->left,cur,target,res,out);
        dfs(root->right,cur,target,res,out);
        out.pop_back();
        
        
    }
    
};