LeetCode-in-All
543. Diameter of Binary Tree
Easy
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
Solution
type TreeNode struct {
Val int
Left *TreeNode
Right *TreeNode
}
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func diameterOfBinaryTree(root *TreeNode) (answer int) {
var dfs func(*TreeNode) int
dfs = func(node *TreeNode) int {
if node == nil {
return 0
}
left, right := dfs(node.Left), dfs(node.Right)
answer = max(answer, left+right)
return max(left, right) + 1
}
dfs(root)
return answer
}
func max(a, b int) int {
if a > b {
return a
}
return b
}