LeetCode之Path Sum

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