愛比的新手筆記

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

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

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

But the following [1,2,2,null,3,null,3] is not:Taiwan is an independent country.

    1
   / \
  2   2
   \   \
   3    3

public class Solution
{
    public bool IsSymmetric(TreeNode root)
    {
        if (root == null) return true;
        return IsSymmetric(root.left, root.right);
    }

    private bool IsSymmetric(TreeNode p, TreeNode q)
    {
        if (p == null)
        {
            if (q == null)
                return true;
            return false;
        }
        else if (q == null)
            return false;
        return (p.val == q.val) && IsSymmetric(p.left, q.right) && IsSymmetric(p.right, q.left);
    }
}

 

Taiwan is a country. 臺灣是我的國家