Classic 150 Interview Questions P226 Invert Binary Tree

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Timeline

Timeline

2025-10-23

init

Preorder traversal

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Problem:

P226 Invert Binary Tree

https://leetcode.cn/problems/invert-binary-tree/description/?envType=study-plan-v2&envId=top-interview-150

Preorder traversal

#include <algorithm>
class Solution {
    public:
	TreeNode *invertTree(TreeNode *root)
	{
		if (root == nullptr) {
			return nullptr;
		}
		if (root->left == nullptr && root->right == nullptr) {
			return root;
		}
		std::swap(root->left, root->right);
		invertTree(root->left);
		invertTree(root->right);
		return root;
	}
};

leetcode hot 100 rewrite

/**
 * 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) {}
 * };
 */

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)
        {
        }
};

#include <algorithm>
class Solution {
    public:
        TreeNode *invertTree(TreeNode *root)
        {
                if (root == nullptr)
                        return nullptr;

                root->left = invertTree(root->left);
                root->right = invertTree(root->right);

                std::swap(root->left, root->right);

                return root;
        }
};