【Maximum Depth of Binary Tree 】cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
            if (!root) return 0;
            if ( !root->left && !root->right ) return 1;
            return std::max(Solution::maxDepth(root->left)+1, Solution::maxDepth(root->right)+1);
    }
};