题目：

题解：

class Solution {
public:
    bool hasPathSum(TreeNode *root, int sum) {
        if (root == nullptr) {
            return false;
        }
        if (root->left == nullptr && root->right == nullptr) {
            return sum == root->val;
        }
        return hasPathSum(root->left, sum - root->val) ||
               hasPathSum(root->right, sum - root->val);
    }
};