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package Algorithms;

import java.util.ArrayDeque;

import Algorithms.tree.TreeNode;

public class IsSymmetric {

public boolean isSymmetric(TreeNode root) {

if (root == null) {

return true;

}

if (root.left == null && root.right == null) {

return true;

} else if (root.left == null || root.right == null) {

return false;

}

// left and right are both not null

ArrayDeque<TreeNode> queueL = new ArrayDeque<TreeNode>();

ArrayDeque<TreeNode> queueR = new ArrayDeque<TreeNode>();

queueL.offer(root.left);

queueR.offer(root.right);

int num = 1;

while (num != 0) {

TreeNode l = queueL.poll();

TreeNode r = queueR.poll();

if (l != null && r != null) { // if they are all not null

if (l.val != r.val) {

return false;

}

queueL.offer(l.left);

queueL.offer(l.right);

queueR.offer(r.right);

queueR.offer(r.left);

num += 4;

} else if (l == null || r == null) {

return false;

}

}

return true;

}

}