/// <summary>
/// OnePass 翻转链表
/// </summary>
/// <param name="head"></param>
/// <param name="m"></param>
/// <param name="n"></param>
/// <returns></returns>
public LinkedNode ReverseBetween(LinkedNode head, int m, int n)
{
if (head == null || head.Next == null)
{
return(head);
}
LinkedNode curr = head;
LinkedNode prev = null;
while (m > 1)
{
prev = curr;
curr = curr.Next;
m--;
n--;
}
LinkedNode front = null;
LinkedNode tail = curr;
while (n > 0)
{
LinkedNode next = curr.Next;
curr.Next = front;
front = curr;
curr = next;
n--;
}
if (prev != null)
{
prev.Next = front;
}
else
{
head = front;
}
tail.Next = curr;
return(head);
}
/// <summary>
/// 倒插法 翻转链表
/// </summary>
/// <param name="head"></param>
/// <param name="startIndex"></param>
/// <param name="endIndex"></param>
/// <returns></returns>
public static LinkedNode RevserseLinkedList(LinkedNode head, int startIndex, int endIndex)
{
if (head == null)
{
return(null);
}
var dummyHead = new LinkedNode(0, head);
var preNode = dummyHead;
var currentNode = head;
for (int index = 0; index < startIndex; index++)
{
if (currentNode == null)
{
return(head);
}
currentNode = currentNode.Next;
preNode = preNode.Next;
}
int length = endIndex - startIndex;
for (int index = 0; index < length; index++)
{
var nextNode = currentNode.Next;
if (nextNode == null)
{
break;
}
currentNode.Next = currentNode.Next.Next;
nextNode.Next = preNode.Next;
preNode.Next = nextNode;
}
return(dummyHead.Next);
}