/// <summary>
/// Function to push an element to the stack
/// </summary>
/// <param name="myStack">Stack</param>
/// <param name="newData">Integer which would be inserted in to stack</param>
public void Push(MyStack myStack, int newData)
{
//Allocate DLLNode and put in data
DLLNode newDllNode = new DLLNode(newData);
//Since we are adding at the beginning, prev is always NULL
newDllNode.prev = null;
// link the old list off the new DLLNode
newDllNode.next = myStack.head;
//Increment count of items in stack
myStack.count += 1;
/* Change mid pointer in two cases
* 1) Linked List is empty.
* 2) Number of nodes in linked list is odd.
*/
if (myStack.count == 1)
{
myStack.mid = newDllNode;
}
else
{
myStack.head.prev = newDllNode;
if ((myStack.count % 2) != 0) // Update mid if ms->count is odd.
{
myStack.mid = myStack.mid.prev;
}
}
//move head to point to the new DLLNode.
myStack.head = newDllNode;
}
/// <summary>
/// Function to pop an element from stack.
/// </summary>
/// <param name="ms">Stack List</param>
/// <returns>The data it removed from the stack</returns>
public int Pop(MyStack ms)
{
// Stack underflow
if (ms.count == 0)
{
Console.WriteLine("Cannot pop as the stack is empty");
return(-1);
}
DLLNode head = ms.head;
int item = head.data;
ms.head = head.next;
// If linked list doesn't become empty, update prev of new head as NULL
if (ms.head != null)
{
ms.head.prev = null;
}
ms.count -= 1;
// update the mid pointer when we have even number of elements in the stack, i,e move down the mid pointer.
if (ms.count % 2 == 0)
{
ms.mid = ms.mid.next;
}
return(item);
}
