数据结构与算法回顾之栈和队列

1. 栈是一种数据项按序排列的数据结构，只能在一端(称为栈顶(top))对数据项进行插入和删除。栈具有“后进先出”特点。

栈实现代码：

namespace System2.Collections.Generic
{

/// <summary>

/// 堆栈类

/// </summary>

/// <typeparam name="T">.net支持类型</typeparam>

public class Stack<T>
{
private List<T> pool = new List<T>();

public Stack() { }

public Stack(int n)

{
	pool = new List<T>(n);
}

public void Clear()
{
	pool.Clear();
}

public bool IsEmpty()
{
	return pool.Count == 0;
}

public T Peek()
{
	if (IsEmpty())

	{
		throw new Exception("堆栈为空！");
	}
	return pool[pool.Count - 1];
}

public T Pop()
{
	if (IsEmpty())

	{
		throw new Exception("堆栈为空！");
	}

	T tmp = pool[pool.Count - 1];

	pool.RemoveAt(pool.Count - 1);

	return tmp;
}

public void Push(T element)
{
	pool.Add(element);
}

public string ToString()
{
	return pool.ToString();
}
}
}

2. 队列是一种特殊的线性表，它只允许在表的前端（front）进行删除操作，而在表的后端（rear）进行插入操作。进行插入操作的端称为队尾，进行删除操作的端称为队头。队列中没有元素时，称为空队列。队列具有“先进先出”的特点。

队列实现代码：

namespace System2.Collections.Generic

{

/// <summary>

/// 队列类

/// </summary>

/// <typeparam name="T">.net支持类型</typeparam>

public class Queue<T>
{
private int first, last, size;
private T[] storage;
public Queue():this(100)
{
}

public Queue(int n)
{
	size = n;
	storage = new T[size];
	first = last = -1;
}

public bool IsFull()
{
	return first == 0 && last == size - 1 || first == last + 1;
}

public bool IsEmpty()
{
	return first == -1;
}

public void Enqueue(T element)
{
	if (last == size - 1 || last == -1)
	{
		storage[0] = element;

		last = 0;

		if (first == -1)
		{
			first = 0;
		}
	}
	else
	{
		storage[++last] = element;
	}
}

public T Dequeue()
{
	T tmp = storage[first];
	if (first == last)
	{
		last = first = -1;
	}
	else if (first == size - 1)
	{
		first = 0;
	}
	else
	{
		first++;
	}

	return tmp;
}

}

}