LeetCode 687 Longest Univalue Path | Python Solution

 LeetCode : https://leetcode.com/problems/longest-univalue-path/

Youtube Solution : Youtube Solution Link

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    longest_path = 0
    def longestUnivaluePath(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        self.helper(root)
        return self.longest_path 

    def helper(self,root) :
        if root is None :
            return 0 

        left = self.helper(root.left)  
        right = self.helper(root.right)    

        if root.left and root.left.val == root.val :
            left_path = 1 + left 
        else:
            left_path = 0

        if root.right and root.right.val == root.val:
            right_path = 1 + right
        else:
            right_path = 0   

        self.longest_path = max(self.longest_path,(left_path+right_path))

        return max(left_path , right_path)