// Search for element in skip list
private Tuple <SkipNode <T>, SkipNode <T>[]> SearchNode(T data)
{
var current = head;
// create update array and initialize it
var update = new SkipNode <T> [Size + 1];
// start from highest level of skip list
for (int i = level; i >= 0; i--)
{
// Move the current pointer forward while key is greater than key of node next to current
while (current.Forward[i] != null && current.Forward[i].Data.CompareTo(data) < 0)
{
current = current.Forward[i];
}
// Insert current in update and move one level down and continue search
update[i] = current;
}
// reached level 0 and forward pointer to right,
// which is desired position to insert key.
current = current.Forward[0];
return(new Tuple <SkipNode <T>, SkipNode <T>[]>(current, update));
}
public SkipList(int size, double fraction = 0.5)
{
Size = size;
Fraction = fraction;
level = 0;
head = new SkipNode <T>(default(T), Size);
}
public void Insert(T data)
{
var searchResult = SearchNode(data);
var current = searchResult.Item1;
var update = searchResult.Item2;
// if current is NULL that means we have reached to end of the level
// or current's key is not equal to key to insert
// that means we have to insert node between update[0] and current node
if (current == null || !current.Data.Equals(data))
{
// Generate a random level for node
int rlevel = RandomLevel();
// If random level is greater than list's current
// level (node with highest level inserted in
// list so far), initialize update value with pointer
// to header for further use
if (rlevel > level)
{
for (int i = level + 1; i < rlevel + 1; i++)
{
update[i] = head;
}
// Update the list current level
level = rlevel;
}
// create new node with random level generated
var n = new SkipNode <T>(data, rlevel);
// insert node by rearranging pointers
for (int i = 0; i <= rlevel; i++)
{
n.Forward[i] = update[i].Forward[i];
update[i].Forward[i] = n;
}
}
}
