题解 | #判断是不是平衡二叉树#

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param pRoot TreeNode类 
# @return bool布尔型
#
class Solution:
    def IsBalanced_Solution(self , pRoot: TreeNode) -> bool:
        if not pRoot:
            return True
        res = self.dfs(pRoot, -1)

        if res == -1:
            return False
        else:
            return True

    def dfs(self, pRoot, count: int):
        count += 1
        if not pRoot.left and not pRoot.right:
            return count
        res1 = count
        res2 = count
        if pRoot.left:
            res1 = self.dfs(pRoot.left, count)
        if pRoot.right:
            res2 = self.dfs(pRoot.right, count)
        if res1 == -1 or res2 == -1:
            return -1
        if abs(res1 - res2) <=1:
            return max(res1, res2)
        else:
            return -1