leetcode101. 对称二叉树

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