StackBasedQueue.cs

usingSystem;
usingSystem.Collections.Generic;

namespaceDataStructures.Queue;

/// <summary>
/// Implementation of a stack based queue. FIFO style.
/// </summary>
/// <remarks>
/// Enqueue is O(1) and Dequeue is amortized O(1).
/// </remarks>
/// <typeparam name="T">Generic Type.</typeparam>
publicclassStackBasedQueue<T>
{
privatereadonlyStack<T>input;
privatereadonlyStack<T>output;

/// <summary>
/// Initializes a new instance of the <see cref="StackBasedQueue{T}" /> class.
/// </summary>
publicStackBasedQueue()
{
input=newStack<T>();
output=newStack<T>();
}

/// <summary>
/// Clears the queue.
/// </summary>
publicvoidClear()
{
input.Clear();
output.Clear();
}

/// <summary>
/// Returns the first item in the queue and removes it from the queue.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown if the queue is empty.</exception>
publicTDequeue()
{
if(input.Count==0&&output.Count==0)
{
thrownewInvalidOperationException("The queue contains no items.");
}

if(output.Count==0)
{
while(input.Count>0)
{
varitem=input.Pop();
output.Push(item);
}
}

returnoutput.Pop();
}

/// <summary>
/// Returns a boolean indicating whether the queue is empty.
/// </summary>
publicboolIsEmpty()=>input.Count==0&&output.Count==0;

/// <summary>
/// Returns a boolean indicating whether the queue is full.
/// </summary>
publicboolIsFull()=>false;

/// <summary>
/// Returns the first item in the queue and keeps it in the queue.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown if the queue is empty.</exception>
publicTPeek()
{
if(input.Count==0&&output.Count==0)
{
thrownewInvalidOperationException("The queue contains no items.");
}

if(output.Count==0)
{
while(input.Count>0)
{
varitem=input.Pop();
output.Push(item);
}
}

returnoutput.Peek();
}

/// <summary>
/// Adds an item at the last position in the queue.
/// </summary>
publicvoidEnqueue(Titem)=>input.Push(item);
}