[leetcode]Symmetric Tree

public class Solution {
public boolean isSymmetric(TreeNode root) {
// Start typing your Java solution below
// DO NOT write main() function
if (root == null) return true;
return (isMirror(root.left, root.right));
}

public boolean isMirror(TreeNode p, TreeNode q) {
if (p == null && q == null) return true;
if (p != null && q != null &&
q.val == p.val &&
isMirror(p.left, q.right) &&
isMirror(p.right, q.left)) {
return true;
}

return false;
}
}

public class Solution {
public boolean isSymmetric(TreeNode root) {
// Start typing your Java solution below
// DO NOT write main() function

if (root == null) return true;
if (root.left == null && root.right == null) return true;
if (root.left == null || root.right == null) return false;

LinkedList<TreeNode> lq = new LinkedList<TreeNode>();
LinkedList<TreeNode> rq = new LinkedList<TreeNode>();

lq.offer(root.left);
rq.offer(root.right);

while (lq.size() != 0 && rq.size() != 0) {
TreeNode ln = lq.poll();
TreeNode rn = rq.poll();

if (ln == null && rn == null) continue;
if (ln == null || rn == null) return false;
if (ln.val != rn.val) return false;

lq.offer(ln.left);
lq.offer(ln.right);
rq.offer(rn.right);
rq.offer(rn.left);
}

return true;
}
}