Coding Mines: Invert Binary Tree LeetCode

Given the root of a Binary Tree, invert the tree, and return its root.

Example 1:

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]

Example 2:

Input: root = [2,1,3]
Output: [2,3,1]

Example 3:

Input: root = []
Output: []

NOTE:

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.

This problem is popular in LeetCode, StackOverFlow and several other forums - Ref 1 A collection of hundreds of interview questions and solutions are available in our blog at Interview Question Solutions

Solution:

	/**
	*
	* Invert a binary tree.
	4
	/ \
	2 7
	/ \ / \
	1 3 6 9
	to
	4
	/ \
	7 2
	/ \ / \
	9 6 3 1
	*
	*
	* Solution:
	* The basic idea here is to switch the right and left child of a node. This process should recursively applied
	* to all the nodes which have the child nodes.
	*
	*
	* @author rbaral
	*/
	public class InvertBinaryTree {
	TreeNode root = null;

	public InvertBinaryTree(){

	}

	public TreeNode invertTree(TreeNode node){
	if(node==null){
	return node;
	}else{
	TreeNode n = node.left;
	node.left = node.right;
	node.right = n;
	invertTree(node.left);
	invertTree(node.right);
	}
	return node;
	}


	public static void main(String args[]){
	InvertBinaryTree inv = new InvertBinaryTree();
	//lets create a binary tree
	TreeNode btree = new TreeNode(4);
	TreeNode lvl1_left = new TreeNode(2);
	TreeNode lvl1_right = new TreeNode(7);
	btree.left = lvl1_left;
	btree.right = lvl1_right;

	TreeNode lvl2_left_l = new TreeNode(1);
	TreeNode lvl2_left_r = new TreeNode(3);
	lvl1_left.left = lvl2_left_l;
	lvl1_left.right = lvl2_left_r;

	TreeNode lvl2_right_l = new TreeNode(6);
	TreeNode lvl2_right_r = new TreeNode(9);
	lvl1_right.left = lvl2_right_l;
	lvl1_right.right = lvl2_right_r;

	btree.printInOrderTree();

	TreeNode invTree = inv.invertTree(btree);
	invTree.printInOrderTree();
	}



	}

Coding Mines