/**

* time: O(n)

* space: O(n)

*/

import java.util.*;

/**

* 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) {

breadthFirstSearch(root);

return root;

}

public void breadthFirstSearch(TreeNode node){

Deque<TreeNode> queue = new ArrayDeque<>();

if (node != null){

queue.add(node);

}

while (!queue.isEmpty()){

TreeNode cur = queue.remove();

TreeNode tmp = cur.left;

cur.left = cur.right;

cur.right = tmp;

if (cur.left != null){

queue.add(cur.left);

}

if (cur.right != null){

queue.add(cur.right);

}

}

}

}