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90 lines
1.4 KiB
Markdown
90 lines
1.4 KiB
Markdown
# [110. Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/)
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## 题目
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Given a binary tree, determine if it is height-balanced.
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For this problem, a height-balanced binary tree is defined as:
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a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
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**Example 1**:
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Given the following tree [3,9,20,null,null,15,7]:
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```
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3
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/ \
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9 20
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/ \
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15 7
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```
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Return true.
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**Example 2**:
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Given the following tree [1,2,2,3,3,null,null,4,4]:
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```
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1
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/ \
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2 2
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/ \
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3 3
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/ \
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4 4
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```
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Return false.
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## 题目大意
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判断一棵树是不是平衡二叉树。平衡二叉树的定义是：树中每个节点都满足左右两个子树的高度差 <= 1 的这个条件。
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## 解题思路
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根据定义判断即可，计算树的高度是第 104 题。
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## 代码
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```go
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package leetcode
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/**
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* Definition for a binary tree node.
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* type TreeNode struct {
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* Val int
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* Left *TreeNode
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* Right *TreeNode
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* }
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*/
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func isBalanced(root *TreeNode) bool {
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if root == nil {
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return true
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}
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leftHight := depth(root.Left)
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rightHight := depth(root.Right)
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return abs(leftHight-rightHight) <= 1 && isBalanced(root.Left) && isBalanced(root.Right)
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}
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func depth(root *TreeNode) int {
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if root == nil {
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return 0
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}
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return max(depth(root.Left), depth(root.Right)) + 1
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}
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``` |