C#语言学习之旅(9)--集合

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当元素的个数是动态的，就应使用集合类，集合类一般有List<T>,ArrayList、数组、队列、堆栈、链表等。下面来介绍各种集合的使用方法。

9.1 列表

对象类型的集合主要位于System.collections命名空间中；泛型集合主要是在System.collections.Generic命名空间中，当然List <T>肯定也都在给命名空间下，下面来介绍列表的使用

1.列表初始化

List<int> intList = new List<int>() { 1, 2 };

定义一个int类型的列表。

2.添加一个元素

intList.Add(3);

3.添加多个元素

intList.AddRange(new int[] { 4, 5 });

AddRange方法的参数是一个IEnumerable<T>类型的对象，当然也可以传送一个数组，上面示例即传送数组。

4.访问元素

访问元素和访问数组很类似的，主要是list<T>都提供了一个索引器，也就是继承了ICollection接口，由于已经提供了索引器了，那么我们就可以像访问数组那样访问数据。

int i=intList[0];

5.遍历数据

一种是可以使用for来循环迭代集合中的每个元素，使用索引器来访问数据，另一种是使用ForEach主要是Ilist<T>同时也继承了接口IEnumerable，该接口主要是用来迭代数据的。

如下面代码：

Console.WriteLine("For Loop");
for (int i = 0; i < intList.Count;i++)
{
Console.WriteLine(intList[i]);
}
Console.WriteLine("ForEach Loop");
foreach(int i in intList)
{
Console.WriteLine(i.ToString());
}

9.2 队列

队列是其元素以先进先出的方式处理集合。先放进在队列的元素会先读取。队列的例子很多的，我们常见的就是排队，排在前面的先服务，后来的后服务。

队列和列表的主要区别在于队列没有执行IList接口，所有不能用索引器访问队列。只能添加元素，下面给出个例子来：

队列demo

    //队列的使用
   public class DocumentManager
   {
      private readonly Queue<Document> documentQueue = new Queue<Document>();//定义一个只读的队列

      public void AddDocument(Document doc)
      {
         lock (this)
         {
            documentQueue.Enqueue(doc);//队列尾部添加元素
         }
      }

      public Document GetDocument()
      {
         Document doc = null;
         lock (this)
         {
            doc = documentQueue.Dequeue();//队列头部获得元素
         }
         return doc;
      }

      public bool IsDocumentAvailable
      {
         get
         {
            return documentQueue.Count > 0;//判断队列是否有元素
         }
      }
   }

9.3 栈

栈和队列是非常相似的集合，只是栈是后进先出而已。

栈Demo

     Stack<char> alphalist = new Stack<char>();
            alphalist.Push('A');
            alphalist.Push('B');

            foreach(char a in alphalist)
            {
                Console.WriteLine(a);
            }

说明：由上面的例子可以得出，输入A,B,输出结果为B，A，那么可以得出栈是后进先出。

9.4 链表

LinkedList<T>是一个双向链表，其元素指向他的前后的元素。链表的优点是，能够快速插入列表中间的数据。缺点就是查找速度比较慢。

9.5 有序表

SortList<TKey,Tvalue>，这个类按照键值给元素排序

有序表demo

SortedList<string, string> sortList = new SortedList<string, string>();
            sortList.Add("1", "demo");
            sortList.Add("2", "demo2");

            foreach(KeyValuePair<string,string> m in sortList)
            {
                Console.WriteLine("{0},{1}", m.Key, m.Value);
            }

9.6 字典

字典表示一种复杂的数据结构。字典也成为隐射或散列表。字典的特性是能够快速查找值，也可以自由添加和删除元素。并且没有在内存中移动后续元素的性能开销。

用作字典中的键的类型必须重写object类得GetHashCode方法。只要字典类需要确定元素的位置，就要调用GetHashCode方法。该方法返回的Int由字典用于计算放置元素的索引。另外键类型还必须执行IEquality.Equals的方法或重写object的equals方法，主要是防止不同键值对象可能返回相同的散列码，所以字典使用Equals方法来比较键。下面给出个示例：

字典demo

  [Serializable]
   public struct EmployeeId  : IEquatable<EmployeeId>
   {
      private readonly char prefix;
      private readonly int number;

      public EmployeeId(string id)
      {
         if (id == null) throw new ArgumentNullException("id");

         prefix = (id.ToUpper())[0];
         int numLength = id.Length - 1;
         number = int.Parse(id.Substring(1, numLength > 6 ? 6 : numLength));
      }

      public override string ToString()
      {
         return prefix.ToString() + string.Format("{0,6:000000}", number);
      }


      public override int GetHashCode()
      {
         return (number ^ number << 16) * 0x15051505;
      }

      public bool Equals(EmployeeId other)
      {
         return (prefix == other.prefix && number == other.number);
      }

       public override bool Equals(object obj)
       {
           if (!(obj is EmployeeId)) return false;
           return Equals((EmployeeId)obj);
       }

       public static bool operator ==(EmployeeId emp1, EmployeeId emp2)
       {
           return emp1.Equals(emp2);
       }

       public static bool operator !=(EmployeeId emp1, EmployeeId emp2)
       {
           return !emp1.Equals(emp2);
       }

   }

   [Serializable]
   public class Employee
   {
      private string name;
      private decimal salary;
      private readonly EmployeeId id;

      public Employee(EmployeeId id, string name, decimal salary)
      {
         this.id = id;
         this.name = name;
         this.salary = salary;
      }

      public override string ToString()
      {
         return String.Format("{0}: {1, -20} {2:C}", id.ToString(), name, salary);
      }
   }

class Program
   {
      static void Main()
      {
         System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");
         Dictionary<EmployeeId, Employee> employees =
               new Dictionary<EmployeeId, Employee>(31);

         EmployeeId idJeff = new EmployeeId("C7102");
         Employee jeff = new Employee(idJeff, "Jeff Gordon",
               5164580.00m);
         employees.Add(idJeff, jeff);
         Console.WriteLine(jeff);

         EmployeeId idTony = new EmployeeId("C7105");
         Employee tony = new Employee(idTony, "Tony Stewart", 4814200.00m);
         employees.Add(idTony, tony);
         Console.WriteLine(tony);

         EmployeeId idDenny = new EmployeeId("C8011");
         Employee denny = new Employee(idDenny, "Denny Hamlin", 3718710.00m);
         employees.Add(idDenny, denny);
         Console.WriteLine(denny);

         EmployeeId idCarl = new EmployeeId("F7908");
         Employee carl = new Employee(idCarl, "Carl Edwards", 3285710.00m);
         employees[idCarl] = carl;
         Console.WriteLine(carl);

         EmployeeId idMatt = new EmployeeId("F7203");
         Employee matt = new Employee(idMatt, "Matt Kenseth", 4520330.00m);
         employees[idMatt] = matt;
         Console.WriteLine(matt);

         while (true)
         {
            try
            {
               Console.Write("Enter employee id (X to exit)> ");
               string userInput = Console.ReadLine();
               userInput = userInput.ToUpper();
               if (userInput == "X") break;
               EmployeeId id = new EmployeeId(userInput);

               Employee employee;
               if (!employees.TryGetValue(id, out employee))
               {
                  Console.WriteLine("Employee with id {0} does not exist",
                     id);
               }
               else
               {
                  Console.WriteLine(employee);
               }
            }
            catch (Exception ex)
            {
               Console.WriteLine("Error: " + ex.Message);
            }
         }

      }

   }

9.7 HashSet

这个集合类包含了不重复项的无序列表。能够很方便的插入元素，该类还提供合集和交集。下面给出简单例子：

哈希集合demo

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Wrox.ProCSharp.Collections
{
   class Program
   {
      static void Main()
      {
         HashSet<string> companyTeams = new HashSet<string>() { "Ferrari", "McLaren", "Toyota", "BMW", "Renault", "Honda" };
         HashSet<string> traditionalTeams = new HashSet<string>() { "Ferrari", "McLaren" };
         HashSet<string> privateTeams = new HashSet<string>() { "Red Bull", "Toro Rosso", "Spyker", "Super Aguri" };

          //添加没有重复，返回true
         if (privateTeams.Add("Williams"))
            Console.WriteLine("Williams added");
         if (!companyTeams.Add("McLaren"))
            Console.WriteLine("McLaren was already in this set");

          //子集
         if (traditionalTeams.IsSubsetOf(companyTeams))
         {
            Console.WriteLine("traditionalTeams is a subset of companyTeams");
         }

          //超集
         if (companyTeams.IsSupersetOf(traditionalTeams))
         {
            Console.WriteLine("companyTeams is a superset of traditionalTeams");
         }

         traditionalTeams.Add("Williams");
          //至少有一个元素相同
         if (privateTeams.Overlaps(traditionalTeams))
         {
            Console.WriteLine("at least one team is the same with the traditional and private teams");
         }

         HashSet<string> allTeams = new HashSet<string>(companyTeams);
          //添加全部内容到集合中去
         allTeams.UnionWith(privateTeams);
         allTeams.UnionWith(traditionalTeams);

         Console.WriteLine();
         Console.WriteLine("all teams");
         foreach (var team in allTeams)
         {
            Console.WriteLine(team);
         }

          //从集合中删除该集合中所有的元素
         allTeams.ExceptWith(privateTeams);
         Console.WriteLine();
         Console.WriteLine("no private team left");
         foreach (var team in allTeams)
         {
            Console.WriteLine(team);
         }

      }
   }
}

9.8 位数组

当我们遇到位运算时候，可以使用BitArray类来处理，该类可以重新设置大小，不需要知道位数，类bitArray是一个引用类型，包含一个int数组，每32位使用一个新的整形。主要提供了，或、与、异或操作，以及倒置位的值等方法，下面给出例子：

位数组demo

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using System.Collections.Specialized;

namespace BitArraySample
{
   class Program
   {
      static void BitArrayDemo()
      {
         BitArray bits1 = new BitArray(8);
         bits1.SetAll(true);
         bits1.Set(1, false);
         bits1[5] = false;
         bits1[7] = false;
         Console.Write("initialized: ");
         DisplayBits(bits1);
         Console.WriteLine();

         DisplayBits(bits1);
         bits1.Not();
         Console.Write(" not ");
         DisplayBits(bits1);
         Console.WriteLine();

         BitArray bits2 = new BitArray(bits1);
         bits2[0] = true;
         bits2[1] = false;
         bits2[4] = true;
         DisplayBits(bits1);
         Console.Write(" or ");
         DisplayBits(bits2);
         Console.Write(" : ");
         bits1.Or(bits2);
         DisplayBits(bits1);
         Console.WriteLine();

         DisplayBits(bits2);
         Console.Write(" and ");
         DisplayBits(bits1);
         Console.Write(" : ");
         bits2.And(bits1);
         DisplayBits(bits2);
         Console.WriteLine();

         DisplayBits(bits1);
         Console.Write(" xor ");
         DisplayBits(bits2);
         bits1.Xor(bits2);
         Console.Write(" : ");
         DisplayBits(bits1);
         Console.WriteLine();
      }

      static void BitVectorDemo()
      {

         BitVector32 bits1 = new BitVector32();
         int bit1 = BitVector32.CreateMask();
         int bit2 = BitVector32.CreateMask(bit1);
         int bit3 = BitVector32.CreateMask(bit2);
         int bit4 = BitVector32.CreateMask(bit3);
         int bit5 = BitVector32.CreateMask(bit4);

         bits1[bit1] = true;
         bits1[bit2] = false;
         bits1[bit3] = true;
         bits1[bit4] = true;
         Console.WriteLine(bits1);

         bits1[0xabcdef] = true;
         Console.WriteLine(bits1);


         int received = 0x79abcdef;

         BitVector32 bits2 = new BitVector32(received);
         Console.WriteLine(bits2);
         // sections: FF EEE DDD CCCC BBBBBBBB AAAAAAAAAAAA
         BitVector32.Section sectionA = BitVector32.CreateSection(0xfff);
         BitVector32.Section sectionB = BitVector32.CreateSection(0xff, sectionA);
         BitVector32.Section sectionC = BitVector32.CreateSection(0xf, sectionB);
         BitVector32.Section sectionD = BitVector32.CreateSection(0x7, sectionC);
         BitVector32.Section sectionE = BitVector32.CreateSection(0x7, sectionD);
         BitVector32.Section sectionF = BitVector32.CreateSection(0x3, sectionE);

         Console.WriteLine("Section A: " + IntToBinaryString(bits2[sectionA], true));
         Console.WriteLine("Section B: " + IntToBinaryString(bits2[sectionB], true));
         Console.WriteLine("Section C: " + IntToBinaryString(bits2[sectionC], true));
         Console.WriteLine("Section D: " + IntToBinaryString(bits2[sectionD], true));
         Console.WriteLine("Section E: " + IntToBinaryString(bits2[sectionE], true));
         Console.WriteLine("Section F: " + IntToBinaryString(bits2[sectionF], true));

      }

      static string IntToBinaryString(int bits, bool removeTrailingZero)
      {
         StringBuilder sb = new StringBuilder(32);

         for (int i = 0; i < 32; i++)
         {
            if ((bits & 0x80000000) != 0)
            {
               sb.Append("1");
            }
            else