leetcode-java-101. Symmetric Tree

public class Solution {
public boolean isSymmetric(TreeNode root) {
if(root == null) {
return true;
} else {
return isSame(root.left,root.right);
}
}

public boolean isSame(TreeNode left,TreeNode right) {
if(left == null && right == null) {
return true;
}
if(left == null || right == null) {
return false;
}
if(left.val != right.val) {
return false;
}
return isSame(left.left,right.right) && isSame(left.right,right.left);
}
}

public class Solution {
public boolean isSymmetric(TreeNode root) {
if(root == null) {
return true;
}
Queue<TreeNode> left = new LinkedList<TreeNode>();
Queue<TreeNode> right = new LinkedList<TreeNode>();

if(root.left != null) {
left.offer(root.left);
}
if(root.right != null) {
right.offer(root.right);
}

while(!left.isEmpty() && !right.isEmpty()) {
TreeNode l = left.poll();
TreeNode r = right.poll();

if(r == null && l == null) {
continue;
}
if(r == null || l == null) {
return false;
}
if(l.val != r.val) {
return false;
}
left.offer(l.left);
left.offer(l.right);
right.offer(r.right);
right.offer(r.left);
}

if(left.isEmpty() && right.isEmpty()) {
return true;
} else {
return false;
}
}
}