Add Solution2.java for 0101.Symmetric Tree

Author: huaxu1024

solution/0101.Symmetric Tree/Solution2.java

@@ -0,0 +1,29 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public boolean isSymmetric(TreeNode root) {
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.add(root);
+        queue.add(root);
+        while (!queue.isEmpty()) {
+            TreeNode t1 = queue.poll();
+            TreeNode t2 = queue.poll();
+            if (t1 == null && t2 == null) continue;
+            if (t1 == null || t2 == null) return false;
+            if (t1.val != t2.val) return false;
+            queue.add(t1.left);
+            queue.add(t2.right);
+
+            queue.add(t1.right);
+            queue.add(t2.left);
+        }
+        return true;
+    }
+}