/**
 * 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 result = false;
    void getsum(TreeNode* cur, int targetSum , int sum)
    {
        if(cur==nullptr)return;
        sum += cur->val;
        //找到叶子节点的和与目标相符
        if(cur->left==nullptr && cur->right==nullptr &&sum == targetSum) result = true;
        getsum(cur->left,  targetSum ,  sum);
        getsum(cur->right,  targetSum ,  sum);
    }
    bool hasPathSum(TreeNode* root, int targetSum) {
        if(root==nullptr) return false;
        getsum(root , targetSum , 0);
        return result;
    }
};

/**
 * 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 result = false;
    void back_trak(TreeNode* cur , int targetSum  , int sum)
    {
        if(cur == nullptr || result == true) return;
        if((sum + cur->val) == targetSum && cur->left==nullptr && cur->right==nullptr ) result = true;
        back_trak(cur->left,targetSum , sum + cur->val );
        back_trak(cur->right,targetSum , sum + cur->val );
        return;
    }
    bool hasPathSum(TreeNode* root, int targetSum) {
        if(root == nullptr ) return false;
        back_trak(root , targetSum , 0);
        return result;
    }
};