543. Diameter of Binary Tree

solution543.py

# https://leetcode.com/problems/diameter-of-binary-tree/description/

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    max_path = 0
    def diameterOfBinaryTree(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        self.max_path = 0
        
        self.ioTraverse(root, 0)
        
        return self.max_path
    
    def ioTraverse(self, node, level):
        if not node:
            return 0
        left_depth = self.ioTraverse(node.left, level + 1)
        right_depth = self.ioTraverse(node.right, level + 1)
            
        longest_path_through_myself = (left_depth - level) + (right_depth - level)
            
        self.max_path = max(longest_path_through_myself, self.max_path)
            
        return max(left_depth, right_depth, level)