leetcode-python/0110_Balanced_Binary_Tree.py at master · coldmanck/leetcode-python · GitHub

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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: TreeNode) -> bool:
        # Time O(n) Space O(h)
        def is_balanced(root): # return (is_balanced, depth)
            if not root:
                return True, 0

            left_is_balanced, left_depth = is_balanced(root.left)
            if not left_is_balanced:
                return False, -1
            right_is_balanced, right_depth = is_balanced(root.right)
            if not right_is_balanced:
                return False, -1
            if abs(left_depth - right_depth) > 1:
                return False, -1

            depth = max(left_depth, right_depth) + 1
            return True, depth

        return is_balanced(root)[0]

        '''Solution II (same time & space complexity)'''
        # is_balance = True
        # def height(node, is_balance):
        #     if not is_balance:
        #         return -1, False
        #     if not node:
        #         return 0, True
        #     left_height, is_balance = height(node.left, is_balance)
        #     right_height, is_balance = height(node.right, is_balance)
        #     if abs(left_height - right_height) > 1:
        #         is_balance = False
        #     return 1 + max(left_height, right_height), is_balance
        # height, is_balance = height(root, is_balance)
        # return is_balance