平衡二叉树python(leetcode110)

#110. 平衡二叉树

# 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:
        if not root:
            return True
        # 分情况
        # 左右两颗子树有不同时为平衡二叉树返回false
        if not self.isBalanced(root.left) or not self.isBalanced(root.right):
            return False
        # 每个节点的左右结点高度差大于1时返回false
        elif abs(self.depth(root.left)-self.depth(root.right)) > 1:
            return False
        return True
    
    def depth(self, root):
        # 求节点深度
        if not root:
            return -1
        else:
            return max(self.depth(root.left), self.depth(root.right)) + 1