public void AddAtIndex(int index, int val)
{
if (index > this.GetLength())
{
return;
}
var prev = this.GetNodeAtIndex(index - 1);
var element = new MySinglyLinkedList(val);
if (prev != null)
{
element.Next = prev.Next;
prev.Next = element;
}
else
{
var oldHead = new MySinglyLinkedList(Value)
{
Next = Next
};
Next = oldHead;
Value = val;
}
}
public static MySinglyLinkedList GetTail(this MySinglyLinkedList head)
{
var tail = head;
while (head != null)
{
tail = head;
head = head.Next;
}
return(tail);
}
public static int GetLength(this MySinglyLinkedList head)
{
var length = 0;
while (head != null)
{
head = head.Next;
length++;
}
return(length);
}
public static IEnumerable <int> ValuesToFlatList(this MySinglyLinkedList head)
{
var result = new List <int>();
while (head != null)
{
result.Add(head.Value);
head = head.Next;
}
return(result);
}
public void AddAtTail(int val)
{
var newElement = new MySinglyLinkedList(val);
var tail = this.GetTail();
if (tail.Value == -1)
{
Value = val;
return;
}
tail.Next = newElement;
}
public static MySinglyLinkedList GetNodeAtIndex(this MySinglyLinkedList current, int index)
{
if (index < 0)
{
return(null);
}
for (int i = 0; i < index; i++)
{
current = current.Next;
}
return(current);
}
public static MySinglyLinkedList ReverseIteratively(this MySinglyLinkedList list)
{
MySinglyLinkedList prev = null;
while (list != null)
{
var head = list;
list = list.Next;
head.Next = prev;
prev = head;
}
return(prev);
}
public void DeleteAtIndex(int index)
{
var prev = this.GetNodeAtIndex(index - 1);
if (prev == null)
{
Value = Next?.Value ?? -1;
Next = Next?.Next;
return;
}
var next = prev.Next?.Next;
prev.Next = next;
}
public void AddAtHead(int val)
{
if (Value != -1)
{
var oldHead = new MySinglyLinkedList(Value)
{
Next = Next
};
Next = oldHead;
Value = val;
}
else
{
Value = val;
}
}
public static MySinglyLinkedList GetCycleIntersect(this MySinglyLinkedList head)
{
var firstPointer = head;
var secondPointer = head;
while (firstPointer?.Next != null)
{
firstPointer = firstPointer.Next;
secondPointer = secondPointer?.Next?.Next;
if (firstPointer == secondPointer)
{
return(firstPointer);
}
}
return(null);
}
public static bool IsPalindrome(this MySinglyLinkedList list)
{
if (list == null)
{
return(false);
}
if (list.Next == null)
{
return(true);
}
var original = list;
var fast = list;
var slow = list;
MySinglyLinkedList half = null;
while (fast != null)
{
fast = fast.Next?.Next;
slow = slow.Next;
if (fast?.Next == null)
{
half = slow;
}
}
var halfReversed = half.ReverseIteratively();
while (halfReversed != null)
{
if (original.Value != halfReversed.Value)
{
return(false);
}
halfReversed = halfReversed.Next;
original = original.Next;
}
return(true);
}
public static MySinglyLinkedList ReverseRecursively(this MySinglyLinkedList list)
{
return(GetNext(list, null));
MySinglyLinkedList GetNext(MySinglyLinkedList list, MySinglyLinkedList prev)
{
if (list != null)
{
var head = list;
list = list.Next;
head.Next = prev;
prev = head;
return(GetNext(list, prev));
}
return(prev);
}
}
public static bool HasCycle(this MySinglyLinkedList head)
{
if (head?.Next == null)
{
return(false);
}
if (head.Next == head)
{
return(true);
}
var firstPointer = head;
var secondPointer = head.Next?.Next;
if (secondPointer == null)
{
return(false);
}
while (true)
{
if (firstPointer == secondPointer)
{
return(true);
}
firstPointer = firstPointer.Next;
if (firstPointer == null)
{
return(false);
}
secondPointer = secondPointer.Next?.Next;
if (secondPointer == null)
{
return(false);
}
}
}
