题目链接/文章讲解/视频讲解：https://programmercarl.com/0112.%E8%B7%AF%E5%BE%84%E6%80%BB%E5%92%8C.html

1.感觉这几个题都是在厘清思路，感受回溯的代码过程，让我对于理解return的作用有更深层次的认识，同时也对递归有了更深的认识，等以后会让这些代码变得更精简，也会去体会迭代的思路。

CPP

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool traveral(TreeNode *node , int count){
        if(node->left == NULL && node->right == NULL && count == 0){
            return true;
        }
        if(node->left == NULL && node->right == NULL && count != 0){
            return false;
        }
        if(node->left){
            count -= node->left->val;
            if(traveral(node->left,count)){
                return true;
            }
            count += node->left->val;
        }
        if(node->right){
            count -= node->right->val;
            if(traveral(node->right,count)){
                return true;
            }
            count += node->right->val;
        }
        return false;
        
    }
    bool hasPathSum(TreeNode* root, int targetSum) {
        if(root == NULL) return false;
        return traveral(root,targetSum -root->val);
    }
};