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+/**%0A * Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).%0A */%0A %0A/**%0A * Definition for a binary tree node.%0A * public class TreeNode %7B%0A *     int val;%0A *     TreeNode left;%0A *     TreeNode right;%0A *     TreeNode(int x) %7B val = x; %7D%0A * %7D%0A */%0A %0A// recursive solution%0Apublic class Solution %7B%0A    public boolean isSymmetric(TreeNode root) %7B%0A        if(root == null) return true;%0A        return helper(root.left, root.right);%0A    %7D%0A    %0A    private boolean helper(TreeNode p, TreeNode q) %7B%0A        if(p == null && q == null)  return true;%0A        if(p == null %7C%7C q == null)  return false;%0A        return p.val == q.val && helper(p.left, q.right) && helper(p.right, q.left);%0A    %7D%0A%7D%0A

Create 101.java