MirrorTree

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题目描述[题目链接][https://www.acwing.com/problem/content/description/37/]

输入一个二叉树，将它变换为它的镜像。

样例

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输入树：
      8
     / \
    6  10
   / \ / \
  5  7 9 11

 [8,6,10,5,7,9,11,null,null,null,null,null,null,null,null] 
输出树：
      8
     / \
    10  6
   / \ / \
  11 9 7  5

 [8,10,6,11,9,7,5,null,null,null,null,null,null,null,null]

算法描述

从根节点开始，每次交换其左右子树递归操作直到叶子节点，真个二叉树就变成了其镜像

C++代码

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void mirror(TreeNode* root) {
        if(root==NULL)return ;
        TreeNode* dummy = root->left;
        root->left = root->right;
        root->right = dummy;
        mirror(root->right);
        mirror(root->left);
        return ;
    }
};

java代码

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public void mirror(TreeNode root) {
        if(root==null)return ;
        TreeNode dummy = root.right;
        root.right = root.left;
        root.left = dummy;
        mirror(root.left);
        mirror(root.right);
        return ;
    }
}