Leetcode 101. Symmetric Tree

Posted 2022-12-11 zhangwj0101

Question

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

    1
   / \\
  2   2
 / \\ / \\
3  4 4  3

But the following is not:

    1
   / \\
  2   2
   \\   \\
   3    3

Code

  public boolean judge(TreeNode left, TreeNode right) 
        if (left == null && right == null) 
            return true;
         else if (left == null && right != null || left != null && right == null) 
            return false;
        
        return left.val == right.val && judge(left.left, right.right) && judge(left.right, right.left);

    


    public boolean isSymmetric(TreeNode root) 
        if (root == null) 
            return true;
        

        return judge(root.left, root.right);