栈 递归

二叉树最大深度

https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func maxDepth(root *TreeNode) int {
	if root == nil {
		return 0
	}
	l := maxDepth(root.Left)
	r := maxDepth(root.Right)
	if l > r {
		return l + 1
	} else {
		return r + 1
	}

}

　　二叉树的前中后序遍历