花花酱 LeetCode 965. Univalued Binary Tree

zxi — Sun, 30 Dec 2018 20:07:33 +0000

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:

The number of nodes in the given tree will be in the range [1, 100].
Each node’s value will be an integer in the range [0, 99].

Solution: Recursion

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

C++

// 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);
  }
};

Python3

# 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)

univalue Archives - Huahua's Tech Road

花花酱 LeetCode 965. Univalued Binary Tree

Problem

Solution: Recursion

C++

Python3

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