104. Maximum Depth of Binary Tree

题目

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.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3.

题目大意

要求输出一棵树的最大高度。

解题思路

这一题递归遍历就可，遍历根节点的左孩子的高度和根节点右孩子的高度，取出两者的最大值再加一即为总高度。