
Data Structure

This illustrates a data structure, a means of storing data within a program.

You may see other such structures in the Data Structures category.
 Illustration of FIFO behavior
Task

Implement a FIFO queue.

Elements are added at one side and popped from the other in the order of insertion.



Operations:

   push   (aka enqueue)    - add element
   pop     (aka dequeue)    - pop first element
   empty                             - return truth value when empty


Errors:

   handle the error of trying to pop from an empty queue (behavior depends on the language and platform)


See

   Queue/Usage   for the built-in FIFO or queue of your language or standard library.


See also

 Array
 Associative array: Creation, Iteration
 Collections
 Compound data type
 Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
 Linked list
 Queue: Definition, Usage
 Set
 Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
 Stack


public class FIFO<T>
{
  class Node
  {
    public T Item { get; set; }
    public Node Next { get; set; }
  }
  Node first = null;
  Node last = null;
  public void push(T item)
  {
    if (empty())
    {
      //Uses object initializers to set fields of new node
      first = new Node() { Item = item, Next = null };
      last = first;
    }
    else
    {
      last.Next = new Node() { Item = item, Next = null };
      last = last.Next;
    }
  }
  public T pop()
  {
    if (first == null)
      throw new System.Exception("No elements"); 
    if (last == first)
      last = null;
    T temp = first.Item;
    first = first.Next;
    return temp;
  }
  public bool empty()
  {
    return first == null;
  }
}