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87 lines
1.9 KiB
Markdown
87 lines
1.9 KiB
Markdown
# [543. Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/)
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## 题目
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Given the `root` of a binary tree, return *the length of the **diameter** of the tree*.
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The **diameter** of a binary tree is the **length** of the longest path between any two nodes in a tree. This path may or may not pass through the `root`.
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The **length** of a path between two nodes is represented by the number of edges between them.
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**Example 1:**
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```
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Input: root = [1,2,3,4,5]
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Output: 3
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Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
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```
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**Example 2:**
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```
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Input: root = [1,2]
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Output: 1
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```
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**Constraints:**
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- The number of nodes in the tree is in the range `[1, 104]`.
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- `100 <= Node.val <= 100`
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## 题目大意
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给定一棵二叉树，你需要计算它的直径长度。一棵二叉树的直径长度是任意两个结点路径长度中的最大值。这条路径可能穿过也可能不穿过根结点。
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## 解题思路
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- 简单题。遍历每个节点的左子树和右子树，累加从左子树到右子树的最大长度。遍历每个节点时，动态更新这个最大长度即可。
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## 代码
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```go
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package leetcode
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import (
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"github.com/halfrost/LeetCode-Go/structures"
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)
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// TreeNode define
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type TreeNode = structures.TreeNode
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/**
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* Definition for a binary tree node.
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* type TreeNode struct {
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* Val int
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* Left *TreeNode
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* Right *TreeNode
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* }
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*/
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func diameterOfBinaryTree(root *TreeNode) int {
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result := 0
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checkDiameter(root, &result)
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return result
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}
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func checkDiameter(root *TreeNode, result *int) int {
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if root == nil {
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return 0
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}
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left := checkDiameter(root.Left, result)
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right := checkDiameter(root.Right, result)
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*result = max(*result, left+right)
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return max(left, right) + 1
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}
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func max(a int, b int) int {
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if a > b {
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return a
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}
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return b
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}
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``` |