mirror of
https://github.com/halfrost/LeetCode-Go.git
synced 2025-07-21 23:44:25 +08:00
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/)
|
||
|
||
|
||
## 题目
|
||
|
||
Given the `root` of a binary tree, return *the length of the **diameter** of the tree*.
|
||
|
||
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`.
|
||
|
||
The **length** of a path between two nodes is represented by the number of edges between them.
|
||
|
||
**Example 1:**
|
||
|
||
|
||
|
||
```
|
||
Input: root = [1,2,3,4,5]
|
||
Output: 3
|
||
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
|
||
|
||
```
|
||
|
||
**Example 2:**
|
||
|
||
```
|
||
Input: root = [1,2]
|
||
Output: 1
|
||
|
||
```
|
||
|
||
**Constraints:**
|
||
|
||
- The number of nodes in the tree is in the range `[1, 104]`.
|
||
- `100 <= Node.val <= 100`
|
||
|
||
## 题目大意
|
||
|
||
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。
|
||
|
||
## 解题思路
|
||
|
||
- 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。
|
||
|
||
## 代码
|
||
|
||
```go
|
||
package leetcode
|
||
|
||
import (
|
||
"github.com/halfrost/LeetCode-Go/structures"
|
||
)
|
||
|
||
// TreeNode define
|
||
type TreeNode = structures.TreeNode
|
||
|
||
/**
|
||
* Definition for a binary tree node.
|
||
* type TreeNode struct {
|
||
* Val int
|
||
* Left *TreeNode
|
||
* Right *TreeNode
|
||
* }
|
||
*/
|
||
|
||
func diameterOfBinaryTree(root *TreeNode) int {
|
||
result := 0
|
||
checkDiameter(root, &result)
|
||
return result
|
||
}
|
||
|
||
func checkDiameter(root *TreeNode, result *int) int {
|
||
if root == nil {
|
||
return 0
|
||
}
|
||
left := checkDiameter(root.Left, result)
|
||
right := checkDiameter(root.Right, result)
|
||
*result = max(*result, left+right)
|
||
return max(left, right) + 1
|
||
}
|
||
|
||
func max(a int, b int) int {
|
||
if a > b {
|
||
return a
|
||
}
|
||
return b
|
||
}
|
||
``` |