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.
递归遍历 左子树 和 右子树
一刷：
public int maxDepth(TreeNode root) { if(root == null){ return 0; } int left = maxDepth(root.left); int right = maxDepth(root.right); return Math.max(left , right) +1; }
[leetcode] 104. Maximum Depth of Binary Tree
原文：http://www.cnblogs.com/pulusite/p/5840656.html