对称二叉树牛客网

一棵二叉树满足镜像对称

public class Solution {
    boolean isSymmetrical(TreeNode pRoot)
    {
        if(pRoot == null){
            return true;
        }
        return  isSymmetrical(pRoot.left,pRoot.right);
    }
    boolean isSymmetrical(TreeNode lefttree,TreeNode righttree){
        if(lefttree == null && righttree == null){
            return true;
        }
        if((lefttree == null && righttree != null ) 
           || (lefttree != null && righttree == null )){
            return false;
        }
        return lefttree.val == righttree.val &&
            isSymmetrical(lefttree.left,righttree.right) &&
            isSymmetrical(lefttree.right,righttree.left);
    }
}