C++ 代码

/**
 * 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 hasPathSum(TreeNode* root, int sum) {
        if(!root){
            return false;
        }
        if(!root->left&&!root->right){
            if(sum==root->val){
            return true;
        }else{
            return false;
        }
        }

        return hasPathSum(root->left,   sum-root->val)||hasPathSum(root->right,   sum-root->val);
    }
};