//----交换节点
internal void Swap(DLinkNode <T> a, DLinkNode <T> b)
{
if (a.Next == b)
{
if (a.Previous == null && b.Next != null)
{
a.Next = b.Next;
b.Next.Previous = a;
b.Previous = null;
b.Next = a;
a.Previous = b;
Head = b;
}
else if (a.Previous != null && b.Next == null)
{
b.Next = a;
a.Previous.Next = b;
b.Previous = a.Previous;
a.Next = null;
a.Previous = b;
Tail = a;
}
else if (a.Previous == null && b.Next == null)
{
a.Previous = b;
a.Next = null;
b.Next = a;
b.Previous = null;
Head = b;
Head = a;
}
else
{
a.Next = b.Next;
b.Next.Previous = a;
DLinkNode <T> c = a.Previous;
a.Previous = b;
b.Next = a;
b.Previous = c;
c.Next = b;
}
}
else if (a.Previous == b)
{
if (b.Previous == null && a.Next != null)
{
Remove(b);
Insert(a, b);
Head = a;
}
else if (b.Previous != null && a.Next == null)
{
Remove(a);
Insert(b.Previous, a);
Tail = b;
}
else if (b.Previous == null && a.Next == null)
{
Remove(b);
AddOnTail(b);
Head = a;
Tail = b;
}
else
{
Remove(b);
Insert(a, b);
}
}
else
{
if (a.Previous == null)
{
Remove(a);
Insert(b, a);
Remove(b);
AddOnHead(b);
Head = b;
if (a.Next == null)
{
Tail = a;
}
else
{
}
}
else if (a.Previous != null && b.Next == null)
{
DLinkNode <T> c = a.Previous;
Remove(a);
AddOnTail(a);
Remove(b);
Insert(c, b);
Tail = a;
}
else if (b.Previous == null)
{
Remove(b);
Insert(a, b);
Remove(a);
AddOnHead(a);
Head = a;
if (a.Next == null)
{
Tail = b;
}
}
else if (b.Previous != null && a.Next == null)
{
DLinkNode <T> c = b.Previous;
Remove(b);
AddOnTail(b);
Remove(a);
Insert(c, a);
Tail = b;
}
else
{
DLinkNode <T> Previous = a.Previous;
Remove(a);
Insert(b, a);
Remove(b);
Insert(Previous, b);
}
}
}