翻转二叉树 LeetCode简单题

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。

示例 1:

输入:root = [4,2,7,1,3,6,9]
输出:[4,7,2,9,6,3,1]
示例 2:

输入:root = [2,1,3]
输出:[2,3,1]
示例 3:

输入:root = []
输出:[]

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if (root == nullptr) return nullptr;
        TreeNode *left = invertTree(root->left);
        TreeNode *right = invertTree(root->right);
        root->left = right;
        root->right = left;
        return root;
    }
};

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