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71 lines
1.1 KiB
Markdown
71 lines
1.1 KiB
Markdown
# [101. Symmetric Tree](https://leetcode.com/problems/symmetric-tree/)
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## 题目
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Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).
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For example, this binary tree [1,2,2,3,4,4,3] is symmetric:
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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 4 4 3
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```
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But the following [1,2,2,null,3,null,3] is not:
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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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**Note**:
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Bonus points if you could solve it both recursively and iteratively.
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## 题目大意
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这一题要求判断 2 颗树是否是左右对称的。
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## 解题思路
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- 这道题是几道题的综合题。将根节点的左字数反转二叉树，然后再和根节点的右节点进行比较，是否完全相等。
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- 反转二叉树是第 226 题。判断 2 颗树是否完全相等是第 100 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 isSymmetric(root *TreeNode) bool {
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if root == nil {
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return true
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}
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return isSameTree(invertTree(root.Left), root.Right)
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}
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``` |