543. Diameter of Binary Tree

Easy

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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

# 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 diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
        result = 0
        def recursion(root):
            nonlocal result
            if not root:
                return 0
            left = 0
            if root.left:
                left = recursion(root.left) + 1
            right = 0
            if root.right:
                right = recursion(root.right) + 1
            temp = max(left,right)
            if left+right > result:
                result = left+right
            return temp
        recursion(root)
        return result