LeetCode Q226: 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.

Solution:
Post order traversal.

	/**
	* 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==NULL)
	return root;
	invertTree(root->left);
	invertTree(root->right);
	TreeNode* tmp=root->left;
	root->left=root->right;
	root->right=tmp;
	return root;
	}
	};

view raw Q226InvertBinaryTree.cpp hosted with ❤ by GitHub