Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

 1 class Solution {
 2 public:
 3     int maxDepth(TreeNode *root) {
 4         if(!root) {
 5             return 0;
 6         }
 7         int depth = 1 + max(maxDepth(root->left), maxDepth(root->right));
 8         return depth;
 9     }
10 };