/*请实现一个函数，用来判断一颗二叉树是不是对称的。注意，如果一个二叉树同此二叉树的镜像是同样的，定义其为对称的。*//*public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;    public TreeNode(int val) {        this.val = val;    }}*/public class Solution {    boolean isSymmetrical(TreeNode pRoot) {        if(pRoot==null) return true;        return check(pRoot.left,pRoot.right);    }    boolean check(TreeNode t1,TreeNode t2){        if(t1 == null && t2 ==null) return true;        if(t1 == null || t2 == null) return false;        if(t1.val != t2.val) return false;        return check(t1.left,t2.right) && check(t1.right,t2.left);    }}