110. Balanced Binary Tree
Easy
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.
方法一:递归
这道题是104题的变式题,再求高度的基础上要求平衡树左右子树高度差都小于等于 1。
时间复杂度:o(n) 空间复杂度:o(1)