//method 1, make a small list and large list, then merge them (small.next = large.head). O(N) time, O(1) space
static LinkListNode partition(LinkListNode head, int d)
{
LinkListNode s = null;
LinkListNode sHead = null;
LinkListNode l = null;
LinkListNode lhead = null;
LinkListNode n = head;
while (n != null)
{
LinkListNode next = n.next;
n.next = null; //otherwise stack overflow exception
if (n.data < d)
{
if (s == null)
{
sHead = n;
s = sHead;
}
else
{
s.next = n;
s = n;
}
}
else
{
if (l == null)
{
lhead = n;
l = lhead;
}
else
{
l.next = n;
l = n;
}
}
n = next;
}
if (s == null)
{
return(lhead);
}
else
{
s.next = lhead;
return(sHead);
}
}
public void setNext(LinkListNode n)
{
next = n;
if (this == last)
{
last = n;
}
if (n != null && n.prev != this)
{
n.setPrevious(this);
}
}
public LinkListNode clone()
{
LinkListNode next2 = null;
if (next != null)
{
next2 = next.clone();
}
LinkListNode head2 = new LinkListNode(data, next2, null);
return(head2);
}
{//Partition: Write code to partition a linked list around value x, such that all nodes less than x come before all nodes greater than or equal to x.
//If x is contained within the list, the values of x only need to be after the elements less than x.
static void Main(string[] args)
{
int[] intArray = new int[] { 3, 5, 8, 5, 10, 2, 1 };
LinkListNode first = new LinkListNode(intArray[0]);
LinkListNode head = first;
for (int i = 1; i < intArray.Length; i++)
{
LinkListNode second = new LinkListNode(intArray[i]);
first.next = second;
first = second;
}
Console.WriteLine(head.printForward());
LinkListNode newHead = partition2(head, 5);
Console.WriteLine(newHead.printForward());
}
public LinkListNode(int d, LinkListNode n, LinkListNode p)
{
data = d;
setNext(n);
setPrevious(p);
}