70 lines
1.2 KiB
Markdown
70 lines
1.2 KiB
Markdown
# 翻转二叉树
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## 题目
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给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。
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示例 1：
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输入：root = [4,2,7,1,3,6,9]
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输出：[4,7,2,9,6,3,1]
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示例 2：
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输入：root = [2,1,3]
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输出：[2,3,1]
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示例 3：
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输入：root = []
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输出：[]
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提示：
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树中节点数目范围在 [0, 100] 内
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-100 <= Node.val <= 100
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## 思路
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- 递归
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- 对于每一个节点
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- 为空
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- 返回当前节点 null
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- 不为空
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- 交换左右节点，再返回当前节点
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## 代码
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```java
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* int val;
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* TreeNode left;
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* TreeNode right;
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* TreeNode() {}
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* TreeNode(int val) { this.val = val; }
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* TreeNode(int val, TreeNode left, TreeNode right) {
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* this.val = val;
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* this.left = left;
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* this.right = right;
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* }
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* }
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*/
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class Solution {
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public TreeNode invertTree(TreeNode root) {
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// Special
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if (root == null) return null;
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TreeNode left = invertTree(root.left);
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TreeNode right = invertTree(root.right);
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root.left = right;
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root.right = left;
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return root;
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}
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}
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``` |