[算法]队列

一、队列

　　一种先进先出的数据结构

二、API

　　public class Queue<T> : IEnumerable

　　public Queue()　　　　　　　　　　构造函数

　　public int Size()　　　　　　　　　 队列大小

　　public Boolean IsEmpty()　　　　  队列判空

　　public void EnQueue(T item)　　   入队

　　public T DeQueue()　　　　　　　  出队

三、实现

3.1 数组实现

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;



namespace AlgorithmPartI

{

    public class ArrayQueue<T> : IEnumerable

    {

        private T[] items;

        private int N;

        private int first;

        private int last;



        public ArrayQueue() {

            this.items = new T[2];

            this.N = 0;

            this.first = 0;

            this.last = -1;

        }



        public void Resize(int capacity) {

            if (capacity <= N) throw new ArgumentException();

            T[] temp = new T[capacity];

            for (int i = 0; i < N; i++) {

                temp[i] = items[(i + first) % items.Length];

            }

            items = temp;

            first = 0;

            last = N-1;

        }



        public int Size { get { return N; } }



        public Boolean IsEmpty() {

            return N == 0;

        }



        public void EnQueue(T item) {

            last = ++last % items.Length;

            items[last] = item;

            N++;

            if (N == items.Length) Resize(items.Length * 2);

        }



        public T DeQueue() {

            if (IsEmpty()) throw new InvalidOperationException();

            T item = items[first++];

            first = first % items.Length;

            N--;

            if (N == items.Length/4) Resize(items.Length / 2);

            return item;

        }



        public T Peek() { 

            if (IsEmpty()) throw new InvalidOperationException();

            return items[first];

        }



        public IEnumerator GetEnumerator()

        {

            for (int i = 0; i < N; i++) {

                yield return items[(i + first) % items.Length];

            }

        }



        public override String ToString() {

            StringBuilder builder = new StringBuilder();

            foreach (var q in this) {

                builder.AppendFormat("{0} ", q);

            }

            return builder.ToString();

        }



        public static void main() 

        { 

            #region 队列测试

            ArrayQueue<int> queue = new ArrayQueue<int>();

            queue.EnQueue(1);

            queue.EnQueue(2);

            Console.WriteLine(queue.DeQueue());

            queue.EnQueue(3);

            Console.WriteLine(queue.DeQueue());

            Console.WriteLine(queue.DeQueue());

            queue.EnQueue(4);

            queue.EnQueue(5);

            Console.WriteLine(queue.DeQueue());

            queue.EnQueue(6);

            Console.WriteLine(queue.DeQueue());

            Console.WriteLine(queue.DeQueue());

            #endregion

            Console.ReadKey();

        }

    }

}

View Code

 

3.2 链表实现

using System;

using System.Collections;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

using System.Text;

using System.Threading.Tasks;



namespace AlgorithmPartI

{

    public class LinkNodeQueue<T> : IEnumerable

    {

        private int N;

        private Node first;

        private Node last;



        public LinkNodeQueue() {

            this.N = 0;

            this.first = this.last = null;

        }



        private class Node {

            public T item;

            public Node next;

        }



        public int Size { get { return N; } }



        public Boolean IsEmpty() {

            return N == 0;

        }



        private Boolean IsCorrect() {

            if (N == 0) {

                if (first != null || first != last) return false;

            }

            else if (N == 1) {

                if (first == null || first != last || first.next != null) return false;

            }

            else {

                if (first == null || first.next == null || last.next != null) return false;

            }

            return true;

        }



        public void EnQueue(T item) {

            Node oldLast = last;

            last = new Node();

            last.item = item;

            last.next = null;

            if (IsEmpty()) first = last;

            else oldLast.next = last;

            N++;

            Debug.Assert(IsCorrect());

        }



        public T DeQueue() {

            if (IsEmpty()) throw new InvalidOperationException();

            T item = first.item;

            Node oldFirst = first;

            first = first.next;

            oldFirst = null;

            N--;

            if (IsEmpty()) last = null;

            Debug.Assert(IsCorrect());

            return item;

        }



        public T Peek() { 

            if (IsEmpty()) throw new InvalidOperationException();

            return first.item;

        }



        public IEnumerator GetEnumerator()

        {

            throw new NotImplementedException();

        }



        static void main() { 

            #region 队列测试

            LinkNodeQueue<int> queue = new LinkNodeQueue<int>();

            queue.EnQueue(1);

            queue.EnQueue(2);

            Console.WriteLine(queue.DeQueue());

            queue.EnQueue(3);

            Console.WriteLine(queue.DeQueue());

            Console.WriteLine(queue.DeQueue());

            queue.EnQueue(4);

            queue.EnQueue(5);

            Console.WriteLine(queue.DeQueue());

            queue.EnQueue(6);

            Console.WriteLine(queue.DeQueue());

            Console.WriteLine(queue.DeQueue());

            #endregion

        }

    }

}

View Code

 

四、队列应用