Leetcode101 对称二叉树

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public boolean isSymmetric(TreeNode root) {
        if(root == null)
           return true;
        return symmetric(root,root);
    }

    private boolean symmetric(TreeNode node1,TreeNode node2){
        if(node1 == null && node2 == null)
            return true;
        if(node1 == null || node2 == null)
            return false;
        if(node1.val == node2.val)
            return symmetric(node1.left,node2.right)&&symmetric(node1.right,node2.left);
        return false;
    }

}