2236. Root Equals Sum of Children

EasyLeetCode

You are given the root of a binary tree that consists of exactly 3 nodes: the root, its left child, and its right child.

Return true if the value of the root is equal to the sum of the values of its two children, or false otherwise.

Example 1:

Input: root = [10,4,6]

Output: true

Explanation: The values of the root, its left child, and its right child are 10, 4, and 6, respectively. 10 is equal to 4 + 6, so we return true.

Example 2:

Input: root = [5,3,1]

Output: false

Explanation: The values of the root, its left child, and its right child are 5, 3, and 1, respectively. 5 is not equal to 3 + 1, so we return false.

Constraints:

The tree consists only of the root, its left child, and its right child. -100 <= Node.val <= 100

How to solve the problem

The problem requires us to check whether the value of the root node is equal to the sum of its two child nodes. Since the tree has only three nodes (root, left child, and right child), we can directly compare these values without recursion or complex traversal.

Code

class Solution:
    def checkTree(self, root: Optional[TreeNode]) -> bool:
        return root.right.val + root.left.val == root.val

Complexity

Time complexity: O(1)

No traversal is needed; only direct comparisons of the three nodes.

Space complexity: O(1)

No extra data structures are used.