/**

* <a href="https://leetcode.com/problems/invert-binary-tree/">week10-1. invert-binary-tree </a>

* <li>Description: Design an algorithm to serialize and deserialize a binary tree </li>

* <li>Topics: Tree, Depth-First Search, Breadth-First Search, Binary Tree </li>

* <li>Time Complexity: O(N), Runtime 0ms </li>

* <li>Space Complexity: O(N), Memory 41.28MB </li>

*/

class Solution {

public TreeNode invertTree(TreeNode root) {

if (root == null) return null;

Queue<TreeNode> queue = new LinkedList<>();

queue.offer(root);

while (!queue.isEmpty()) {

TreeNode parent = queue.poll();

TreeNode temp = parent.left;

parent.left = parent.right;

parent.right = temp;

if (parent.left != null) queue.offer(parent.left);

if (parent.right != null) queue.offer(parent.right);

}

return root;

}

}