思路：此题思路为递归实现，递归思路为：在每层递归的过程中将各个节点的数据记录下来，不断将减少目标数据的值准备进行判断，当进行到叶子节点时要进行判断

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
bool hasPathSum(struct TreeNode* root, int targetSum) {
    
    if(root==NULL)
    {
        return false;
    }
    int sum=root->val;
    if(root->left==NULL&&root->right==NULL)
    {
        return targetSum==sum;
    }
   
    return hasPathSum(root->left,targetSum-sum)||hasPathSum(root->right,targetSum-sum);
}