82. Remove Duplicates from Sorted List II

删除链表中重复的结点，只要是有重复过的结点，全部删除。

SLinkedList<int> slist = new SLinkedList<int>();
slist.AppendRange(new[] { 6, 1, 1, 2, 3, 3, 3, 4, 5, 5 });
Console.WriteLine("Before: " + slist.Print());
var rslt = slist.DeleteDuplicates();
Console.WriteLine(" After: " + rslt.Print());

/// <summary>
/// 删除链表中重复的结点，只要是有重复过的结点，全部删除。
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="source"></param>
/// <returns></returns>
public static SLinkedList<T> DeleteDuplicates<T>(this SLinkedList<T> source) where T : IComparable<T>
{
    if (source.IsEmpty())
    {
        return null;
    }
    if (source.Head == null || source.Head.Next == null)
    {
        return source;
    }
    var tmp = new SLinkedList<T>(source);
    var head = DeleteDuplicates(tmp.Head);
    tmp.Clear();
    return new SLinkedList<T>(head);
}

private static SLinkedListNode<T> DeleteDuplicates<T>(SLinkedListNode<T> head) where T : IComparable<T>
{
    if (head == null)
    {
        return null;
    }
    if (head.Next != null && head.IsEqualTo(head.Next))
    {
        while (head.Next != null && head.IsEqualTo(head.Next))
        {
            head = head.Next;
        }
        return DeleteDuplicates(head.Next);
    }
    head.Next = DeleteDuplicates(head.Next);
    return head;
}