花花酱 LeetCode 965. Univalued Binary Tree

Problem

A binary tree is univalued if every node in the tree has the same value.

Return true if and only if the given tree is univalued.

Example 1:

Input: [1,1,1,1,1,null,1]
Output: true

Example 2:

Input: [2,2,2,5,2]
Output: false

Note:

Time complexity: O(n)
Space complexity: O(h)

// Author: Huahua, running time: 0 ms

class Solution {

public:

bool isUnivalTree(TreeNode* root) {

if (!root) return true;

if (root->left && root->val != root->left->val) return false;

if (root->right && root->val != root->right->val) return false;

return isUnivalTree(root->left) && isUnivalTree(root->right);

}

};

# Author: Huahua, running time: 68 ms

class Solution:

def isUnivalTree(self, root):

if not root: return True

if root.left and root.left.val != root.val: return False

if root.right and root.right.val != root.val: return False

return self.isUnivalTree(root.left) and self.isUnivalTree(root.right)

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