0110. Balanced Binary Tree

# 110. Balanced Binary Tree#

## 题目 #

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.

## 代码 #

``````
package leetcode

/**
* Definition for a binary tree node.
* type TreeNode struct {
*     Val int
*     Left *TreeNode
*     Right *TreeNode
* }
*/
func isBalanced(root *TreeNode) bool {
if root == nil {
return true
}
leftHight := depth(root.Left)
rightHight := depth(root.Right)
return abs(leftHight-rightHight) <= 1 && isBalanced(root.Left) && isBalanced(root.Right)
}

func depth(root *TreeNode) int {
if root == nil {
return 0
}
return max(depth(root.Left), depth(root.Right)) + 1
}

``````

Sep 6, 2020