leetcode 226. 翻转二叉树-二叉树

https://leetcode-cn.com/problems/invert-binary-tree/

解题思路:

• 在前序遍历位置进行交换,因为前序是从根节点遍历
• 注意:
  1.递归结束条件

/**
 * 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) {
        // 递归结束条件
        if(root == nullptr)return nullptr;
        // 左右节点交换
        TreeNode* temp = root->left;
        root->left = root->right;
        root->right = temp;
        // 递归调用左右节点
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};