public static ComplexLinkedListNode Execute(ComplexLinkedListNode head)
{
if (head == null)
{
throw new ArgumentNullException(nameof(head), "The input linked list can't be null");
}
//return CopyUsingHash(head);
return(Copy(head));
}
public void LinkedListWithOnlyOneNode()
{
var oldNode = new ComplexLinkedListNode(20);
var newNode = CopyComplexLinkedList.Execute(oldNode);
Assert.Equal(oldNode.Value, newNode.Value);
Assert.NotEqual(oldNode, newNode);
Assert.Null(oldNode.Next);
Assert.Null(newNode.Next);
Assert.Null(oldNode.Sibling);
Assert.Null(newNode.Sibling);
}
private static ComplexLinkedListNode Copy(ComplexLinkedListNode head)
{
// 将每个节点复制后,就接在本节点后面,再往后才是剩下的节点
var currentNode = head;
var nextNode = head.Next;
while (currentNode != null)
{
var newNode = new ComplexLinkedListNode(currentNode.Value);
currentNode.Next = newNode;
newNode.Next = nextNode;
currentNode = nextNode;
nextNode = nextNode?.Next;
}
// 重建sibling关系
currentNode = head;
while (currentNode != null)
{
if (currentNode.Sibling != null)
{
currentNode.Next.Sibling = currentNode.Sibling.Next;
}
currentNode = currentNode.Next.Next;
}
// 拆分出新链表,并且会还原原始链表
var old = head;
var oldToNew = head.Next;
var newHead = oldToNew;
var newCurrent = newHead;
while (oldToNew.Next != null)
{
old.Next = oldToNew.Next;
old = old.Next;
oldToNew = oldToNew.Next.Next;
newCurrent.Next = oldToNew;
newCurrent = newCurrent.Next;
}
// 上面循环结束的时候,原链表最后一个节点指向的是新链表最后一个节点,需要手动指向null,才能完全恢复原始链表
old.Next = null;
return(newHead);
}
// 利用hash关联新旧两个链表中的值,时间效率很高,但是需要占用额外空间
private static ComplexLinkedListNode CopyUsingHash(ComplexLinkedListNode head)
{
var newHead = new ComplexLinkedListNode(head.Value);
Hashtable hash = new Hashtable
{
{ head, newHead }
};
// 复制链表
var oldCurrent = head;
var newCurrent = newHead;
while (oldCurrent.Next != null)
{
oldCurrent = oldCurrent.Next;
newCurrent.Next = new ComplexLinkedListNode(oldCurrent.Value);
newCurrent = newCurrent.Next;
// 记录新旧链表对应节点的关系,这样在第二轮遍历重建Sibling关系时,只需要O(1)的查找时间
hash.Add(oldCurrent, newCurrent);
}
// 重建Sibling关系
oldCurrent = head;
newCurrent = newHead;
while (oldCurrent != null)
{
// 当旧链表节点有Sibling节点时,给新链表也加上对应的关系(通过hash查找加快速度)
if (oldCurrent.Sibling != null)
{
newCurrent.Sibling = (ComplexLinkedListNode)hash[oldCurrent.Sibling];
}
oldCurrent = oldCurrent.Next;
newCurrent = newCurrent.Next;
}
return(newHead);
}
