JuneChallenge (62) | Invert Binary Tree

Invert a binary tree.

Example:

Input:

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

Output:

     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.

Simalar swap two poiter a and b, this problem is easy with dfs:

	/**
	* Definition for a binary tree node.
	* public class TreeNode {
	* int val;
	* TreeNode left;
	* TreeNode right;
	* TreeNode() {}
	* TreeNode(int val) { this.val = val; }
	* TreeNode(int val, TreeNode left, TreeNode right) {
	* this.val = val;
	* this.left = left;
	* this.right = right;
	* }
	* }
	*/
	class Solution {
	public TreeNode invertTree(TreeNode root) {
	if (root == null){
	return null;
	}
	TreeNode left = root.left;
	root.left = invertTree(root.right);
	root.right = invertTree(left);
	return root;
	}
	}

view raw InvertBinaryTree.java delivered with ❤ by emgithub

Thank you !