Definition for a binary tree node.

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Solved at: 220925

Question

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the left and right subtrees of every node differ in height by no more than 1.

Solution

python

# 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 getHeight(self, node):
        if node == None:
            return 0
        l = node.left
        r = node.right
        return max(self.getHeight(l), self.getHeight(r)) + 1

    def isBalanced(self, root: Optional[TreeNode]) -> bool:
        if root == None:
            return True
        l = root.left
        r = root.right
        lh = self.getHeight(l)
        rh = self.getHeight(r)
        return abs(lh - rh) <= 1 and self.isBalanced(l) and self.isBalanced(r)

Results

Runtime

123 ms, faster than 14.05% of Python3 online submissions for Balanced Binary Tree.

Memory Usage

18.6 MB, less than 90.53% of Python3 online submissions for Balanced Binary Tree.

Complexity Analysis

Time

$O(n \log n)$ because worst case, we might need to travel all nodes while counting their height with $O(n)$

Space

$O(n)$ because we require a stack to contain all nodes, worst case.

Definition for a binary tree node.

Question

Solution

Results

Runtime

Memory Usage

Complexity Analysis

Time

Space

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