Problem101.java

class Problem101 {
 public static void main(String[] args) {
 Problem101 p = new Problem101();
 TreeNode root = new TreeNode(1);
 root.left = new TreeNode(2);
 System.out.println(p.isSymmetric(root));
 }

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