LeetCode 226. Invert Binary Tree 题解（C++）

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题目描述

• Invert a binary tree.

示例

• Input:
  4
  / \
  2 7
  / \ / \
  1 3 6 9

• Output:
  4
  / \
  7 2
  / \ / \
  9 6 3 1

思路

• 用递归实现二叉树的翻转。递归出口为当结点为空时，返回NULL。否则对左右子树进行递归翻转，之后对翻转完成的左右子树的位置进行交换即可。

代码

/** * 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:    TreeNode* invertTree(TreeNode* root)     {        if (root == NULL)        {            return NULL;        }        root->left = invertTree(root->left);        root->right = invertTree(root->right);        TreeNode *temp = root->left;        root->left = root->right;        root->right = temp;        return root;    }};