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110. Balanced Binary Tree

Tree Depth-First Search Binary Tree

Problem - Balanced Binary Tree

Easy

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

 

Example 1:

Input: root = [3,9,20,null,null,15,7]
Output: true

Example 2:

Input: root = [1,2,2,3,3,null,null,4,4]
Output: false

Example 3:

Input: root = []
Output: true

 

Constraints:

  • The number of nodes in the tree is in the range [0, 5000].
  • -104 <= Node.val <= 104

Solutions

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# 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 isBalanced(self, root: Optional[TreeNode]) -> bool:
        def height(root: Optional[TreeNode]) -> int:
            if root is None:
                return 0

            left, right = height(root.left), height(root.right)
            if left == -1 or right == -1 or abs(left - right) > 1:
                return -1

            return max(left, right) + 1

        return height(root) >= 0

Submission Stats:

  • Runtime: 3 ms (65.40%)
  • Memory: 19 MB (26.35%)