LeetCode: Maximum Depth of Binary Tree

思路：树的深度 = 左右子树最大的深度 + 1

code:

class Solution {
public:
    int maxDepth(TreeNode *root) {
        if(root)
            return max(maxDepth(root->left), maxDepth(root->right)) + 1;
        return 0;
    }
};