lc110. Balanced Binary Tree

110. Balanced Binary Tree Easy

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Share 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 depth of the two subtrees of every node never differ by more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7

Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4

Return false.

思路：迭代

代码：python3

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # @param {TreeNode} root
    # @return {boolean}
    def isBalanced(self, root):
        if not root:return True
        return abs(self.getHeight(root.left)-self.getHeight(root.right))<2 and self.isBalanced(root.left) and self.isBalanced(root.right)
        
    def getHeight(self,root):
        if not root:return 0
        return 1+max(self.getHeight(root.left),self.getHeight(root.right))