leetcode刷题笔记(Golang)--104. Maximum Depth of Binary Tree

104. 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.

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.

/**
 * 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
	}
	return maxDepthCore(root)
}

func maxDepthCore(root *TreeNode) int {
	if root == nil {
		return 0
	}
	res := 1
	hleft := maxDepthCore(root.Left)
	hright := maxDepthCore(root.Right)
	if hleft > hright {
		res += hleft
	} else {
		res += hright
	}
	return res
}