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
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def __init__(self):
self.diameter = 0
def diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
self.diameter = 0
self.diameterOfBinaryTreeUtil(root)
return self.diameter
def diameterOfBinaryTreeUtil(self, root: TreeNode) -> int:
if root is None:
return 0
leftLength = 1 + self.diameterOfBinaryTreeUtil(root.left) if root.left else 0
rightLength = 1 + self.diameterOfBinaryTreeUtil(root.right) if root.right else 0
self.diameter = max(self.diameter, leftLength + rightLength)
return max(leftLength, rightLength)