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.
思路:
一棵空树的深度为零,也就是可以看做叶子节点的孩子节点的深度为零,叶子节点的深度为1,而一个树的深度和高度相同,所以求一个树的深度其实就是左右子树的深度的最大值加一。递归求解就可以。
代码:
go:
/**
* 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 max(maxDepth(root.Left), maxDepth(root.Right)) + 1
}
func max(i, j int) int {
if i > j {
return i
}
return j
}