LeetCode 226. Invert Binary Tree

Invert a binary tree.

4
/ \
2 7
/ \ / \
1 3 6 9
to
4
/ \
7 2
/ \ / \
9 6 3 1
Trivia:
This problem was inspired by this original tweet by Max Howell:
Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

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

/**

* 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) {

TreeNode* p = root;

if(root == NULL) {

return NULL;

}

TreeNode* temp = root->left;

root->left = root->right;

root->right = temp;

invertTree(root->left);

invertTree(root->right);

return p;

}

};

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