The serialization of a binary tree follows a level order traversal, where ‘#‘ signifies a path terminator where no node exists below.

Here‘s an example:

   1
  /  2   3
    /
   4
         5

答案

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