Invert Binary Tree

Desicription

Invert a binary tree.

Example:

Input:

1
2
3
4
5
4
/ \
2 7
/ \ / \
1 3 6 9

Output:

1
2
3
4
5
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 f* off.

Solution

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/**
* 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 == nullptr) {
return nullptr;
}
auto left_node = invertTree(root->left);
auto right_node = invertTree(root->right);
root->left = right_node;
root->right = left_node;
return root;
}
};