【二叉树-中等】687. 最长同值路径

【题目】

【代码】

# 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 visit(self,root):
        if not root:
            return 
        l=self.visit(root.left)
        r=self.visit(root.right)
        l2,r2=0,0
        if root.left and root.left.val==root.val:
            l2=l+1
        if root.right and root.right.val==root.val:
            r2=r+1
        self.cnt=max(self.cnt,l2+r2)
        # print(root.val," l:",l," r:",r)
        return max(l2,r2)
        
    def longestUnivaluePath(self, root: Optional[TreeNode]) -> int:
        self.cnt=0
        self.visit(root)        
        return self.cnt