ArrayList.BinarySearch 方法

Source:

ArrayList.cs

Source:

ArrayList.cs

Source:

ArrayList.cs

public:
 virtual int BinarySearch(System::Object ^ value);

public virtual int BinarySearch (object value);

public virtual int BinarySearch (object? value);

abstract member BinarySearch : obj -> int
override this.BinarySearch : obj -> int

Public Overridable Function BinarySearch (value As Object) As Integer

参数

返回

如果找到 value，则排序 ArrayList中 value 的从零开始的索引;否则为负数，即下一个大于 value 的元素的索引的按位补数;如果没有较大的元素，则为 Count的按位补数。

例外

示例

下面的代码示例演示如何使用 BinarySearch 在 ArrayList中查找特定对象。

using namespace System;
using namespace System::Collections;
void FindMyObject( ArrayList^ myList, Object^ myObject );
void PrintValues( IEnumerable^ myList );
int main()
{
   
   // Creates and initializes a new ArrayList. BinarySearch requires
   // a sorted ArrayList.
   ArrayList^ myAL = gcnew ArrayList;
   for ( int i = 0; i <= 4; i++ )
      myAL->Add( i * 2 );
   
   // Displays the ArrayList.
   Console::WriteLine( "The Int32 ArrayList contains the following:" );
   PrintValues( myAL );
   
   // Locates a specific object that does not exist in the ArrayList.
   Object^ myObjectOdd = 3;
   FindMyObject( myAL, myObjectOdd );
   
   // Locates an object that exists in the ArrayList.
   Object^ myObjectEven = 6;
   FindMyObject( myAL, myObjectEven );
}

void FindMyObject( ArrayList^ myList, Object^ myObject )
{
   int myIndex = myList->BinarySearch( myObject );
   if ( myIndex < 0 )
      Console::WriteLine( "The object to search for ({0}) is not found. The next larger object is at index {1}.", myObject,  ~myIndex );
   else
      Console::WriteLine( "The object to search for ({0}) is at index {1}.", myObject, myIndex );
}

void PrintValues( IEnumerable^ myList )
{
   IEnumerator^ myEnum = myList->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ obj = safe_cast<Object^>(myEnum->Current);
      Console::Write( "   {0}", obj );
   }

   Console::WriteLine();
}

/* 
 This code produces the following output.
 
 The Int32 ArrayList contains the following:
    0   2   4   6   8
 The object to search for (3) is not found. The next larger object is at index 2.
 The object to search for (6) is at index 3.
 */

using System;
using System.Collections;
public class SamplesArrayList  {

   public static void Main()  {

      // Creates and initializes a new ArrayList. BinarySearch requires
      // a sorted ArrayList.
      ArrayList myAL = new ArrayList();
      for ( int i = 0; i <= 4; i++ )
         myAL.Add( i*2 );

      // Displays the ArrayList.
      Console.WriteLine( "The int ArrayList contains the following:" );
      PrintValues( myAL );

      // Locates a specific object that does not exist in the ArrayList.
      Object myObjectOdd = 3;
      FindMyObject( myAL, myObjectOdd );

      // Locates an object that exists in the ArrayList.
      Object myObjectEven = 6;
      FindMyObject( myAL, myObjectEven );
   }

   public static void FindMyObject( ArrayList myList, Object myObject )  {
      int myIndex=myList.BinarySearch( myObject );
      if ( myIndex < 0 )
         Console.WriteLine( "The object to search for ({0}) is not found. The next larger object is at index {1}.", myObject, ~myIndex );
      else
         Console.WriteLine( "The object to search for ({0}) is at index {1}.", myObject, myIndex );
   }

   public static void PrintValues( IEnumerable myList )  {
      foreach ( Object obj in myList )
         Console.Write( "   {0}", obj );
      Console.WriteLine();
   }
}
/*
This code produces the following output.

The int ArrayList contains the following:
   0   2   4   6   8
The object to search for (3) is not found. The next larger object is at index 2.
The object to search for (6) is at index 3.
*/

Imports System.Collections

Public Class SamplesArrayList    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new ArrayList. BinarySearch requires
        ' a sorted ArrayList.
        Dim myAL As New ArrayList()
        Dim i As Integer
        For i = 0 To 4
            myAL.Add(i * 2)
        Next i 

        ' Displays the ArrayList.
        Console.WriteLine("The Int32 ArrayList contains the following:")
        PrintValues(myAL)
        
        ' Locates a specific object that does not exist in the ArrayList.
        Dim myObjectOdd As Object = 3
        FindMyObject(myAL, myObjectOdd)
        
        ' Locates an object that exists in the ArrayList.
        Dim myObjectEven As Object = 6
        FindMyObject(myAL, myObjectEven)
    End Sub    
    
    Public Shared Sub FindMyObject(myList As ArrayList, myObject As Object)
        Dim myIndex As Integer = myList.BinarySearch(myObject)
        If myIndex < 0 Then
            Console.WriteLine("The object to search for ({0}) is not found. " _
               + "The next larger object is at index {1}.", myObject, _
               Not myIndex)
        Else
            Console.WriteLine("The object to search for ({0}) is at index " _
               + "{1}.", myObject, myIndex)
        End If
    End Sub
     
    Public Shared Sub PrintValues(myList As IEnumerable)
        Dim obj As [Object]
        For Each obj In  myList
            Console.Write("   {0}", obj)
        Next obj
        Console.WriteLine()
    End Sub
    
End Class

' This code produces the following output.
' 
' The Int32 ArrayList contains the following:
'     0    2    4    6    8
' The object to search for (3) is not found. The next larger object is at index 2.
' The object to search for (6) is at index 3.

注解

value 参数和 ArrayList 的每个元素都必须实现用于比较的 IComparable 接口。 ArrayList 的元素必须已根据 IComparable 实现定义的排序顺序按递增值进行排序;否则，结果可能不正确。

将 null 与任何类型进行比较，在使用 IComparable时不会生成异常。 排序时，null 被视为小于任何其他对象。

如果 ArrayList 包含多个具有相同值的元素，该方法只返回其中一个匹配项，并且可能会返回任何一个匹配项，不一定返回第一个。

如果 ArrayList 不包含指定值，该方法将返回负整数。 可以将按位补运算 （~） 应用于此负整数，以获取大于搜索值的第一个元素的索引。 将值插入 ArrayList时，此索引应用作插入点来维护排序顺序。

此方法是 O(log n) 操作，其中 nCount。

另请参阅

• 在集合 中执行 Culture-Insensitive 字符串操作

Source:

ArrayList.cs

Source:

ArrayList.cs

Source:

ArrayList.cs

public:
 virtual int BinarySearch(System::Object ^ value, System::Collections::IComparer ^ comparer);

public virtual int BinarySearch (object value, System.Collections.IComparer comparer);

public virtual int BinarySearch (object? value, System.Collections.IComparer? comparer);

abstract member BinarySearch : obj * System.Collections.IComparer -> int
override this.BinarySearch : obj * System.Collections.IComparer -> int

Public Overridable Function BinarySearch (value As Object, comparer As IComparer) As Integer

参数

返回

如果找到 value，则排序 ArrayList中 value 的从零开始的索引;否则为负数，即下一个大于 value 的元素的索引的按位补数;如果没有较大的元素，则为 Count的按位补数。

例外

示例

以下示例创建彩色动物 ArrayList。 提供的 IComparer 执行二进制搜索的字符串比较。 将显示迭代搜索和二进制搜索的结果。

using namespace System;
using namespace System::Collections;

public ref class SimpleStringComparer : public IComparer
{
    virtual int Compare(Object^ x, Object^ y) sealed = IComparer::Compare
    {
        String^ cmpstr = (String^)x;
        return cmpstr->CompareTo((String^)y);
    }
};

public ref class MyArrayList : public ArrayList
{
public:
    static void Main()
    {
        // Creates and initializes a new ArrayList.
        MyArrayList^ coloredAnimals = gcnew MyArrayList();

        coloredAnimals->Add("White Tiger");
        coloredAnimals->Add("Pink Bunny");
        coloredAnimals->Add("Red Dragon");
        coloredAnimals->Add("Green Frog");
        coloredAnimals->Add("Blue Whale");
        coloredAnimals->Add("Black Cat");
        coloredAnimals->Add("Yellow Lion");

        // BinarySearch requires a sorted ArrayList.
        coloredAnimals->Sort();

        // Compare results of an iterative search with a binary search
        int index = coloredAnimals->IterativeSearch("White Tiger");
        Console::WriteLine("Iterative search, item found at index: {0}", index);

        index = coloredAnimals->BinarySearch("White Tiger", gcnew SimpleStringComparer());
        Console::WriteLine("Binary search, item found at index:    {0}", index);
    }

    int IterativeSearch(Object^ finditem)
    {
        int index = -1;

        for (int i = 0; i < this->Count; i++)
        {
            if (finditem->Equals(this[i]))
            {
                index = i;
                break;
            }
        }
        return index;
    }
};

int main()
{
    MyArrayList::Main();
}
//
// This code produces the following output.
//
// Iterative search, item found at index: 5
// Binary search, item found at index:    5
//

using System;
using System.Collections;

public class SimpleStringComparer : IComparer
{
    int IComparer.Compare(object x, object y)
    {
        string cmpstr = (string)x;
        return cmpstr.CompareTo((string)y);
    }
}

public class MyArrayList : ArrayList
{
    public static void Main()
    {
        // Creates and initializes a new ArrayList.
        MyArrayList coloredAnimals = new MyArrayList();

        coloredAnimals.Add("White Tiger");
        coloredAnimals.Add("Pink Bunny");
        coloredAnimals.Add("Red Dragon");
        coloredAnimals.Add("Green Frog");
        coloredAnimals.Add("Blue Whale");
        coloredAnimals.Add("Black Cat");
        coloredAnimals.Add("Yellow Lion");

        // BinarySearch requires a sorted ArrayList.
        coloredAnimals.Sort();

        // Compare results of an iterative search with a binary search
        int index = coloredAnimals.IterativeSearch("White Tiger");
        Console.WriteLine("Iterative search, item found at index: {0}", index);

        index = coloredAnimals.BinarySearch("White Tiger", new SimpleStringComparer());
        Console.WriteLine("Binary search, item found at index:    {0}", index);
    }

    public int IterativeSearch(object finditem)
    {
        int index = -1;

        for (int i = 0; i < this.Count; i++)
        {
            if (finditem.Equals(this[i]))
            {
                index = i;
                break;
            }
        }
        return index;
    }
}
//
// This code produces the following output.
//
// Iterative search, item found at index: 5
// Binary search, item found at index:    5
//

Imports System.Collections

Public Class SimpleStringComparer
    Implements IComparer

    Function Compare(x As Object, y As Object) As Integer Implements IComparer.Compare
          Dim cmpstr As String = CType(x, String)
          Return cmpstr.CompareTo(CType(y, String))
    End Function
End Class

Public Class MyArrayList
    Inherits ArrayList

    Public Shared Sub Main()
        ' Creates and initializes a new ArrayList.
        Dim coloredAnimals As New MyArrayList()

        coloredAnimals.Add("White Tiger")
        coloredAnimals.Add("Pink Bunny")
        coloredAnimals.Add("Red Dragon")
        coloredAnimals.Add("Green Frog")
        coloredAnimals.Add("Blue Whale")
        coloredAnimals.Add("Black Cat")
        coloredAnimals.Add("Yellow Lion")

        ' BinarySearch requires a sorted ArrayList.
        coloredAnimals.Sort()

        ' Compare results of an iterative search with a binary search
        Dim index As Integer = coloredAnimals.IterativeSearch("White Tiger")
        Console.WriteLine("Iterative search, item found at index: {0}", index)

        index = coloredAnimals.BinarySearch("White Tiger", New SimpleStringComparer())
        Console.WriteLine("Binary search, item found at index:    {0}", index)
    End Sub

    Public Function IterativeSearch(finditem As Object) As Integer
        Dim index As Integer = -1

        For i As Integer = 0 To MyClass.Count - 1
            If finditem.Equals(MyClass.Item(i))
                index = i
                Exit For
            End If
        Next i
        Return index
    End Function
End Class
'
' This code produces the following output.
'
' Iterative search, item found at index: 5
' Binary search, item found at index:    5
'

注解

比较器自定义元素的比较方式。 例如，可以使用 CaseInsensitiveComparer 实例作为比较器来执行不区分大小写的字符串搜索。

如果提供了 comparer，则使用指定的 IComparer 实现将 ArrayList 的元素与指定值进行比较。 ArrayList 的元素必须已根据 comparer定义的排序顺序按递增值进行排序;否则，结果可能不正确。

如果 comparernull，则使用元素本身或指定值提供的 IComparable 实现完成比较。 ArrayList 的元素必须已根据 IComparable 实现定义的排序顺序按递增值进行排序;否则，结果可能不正确。

将 null 与任何类型进行比较，在使用 IComparable时不会生成异常。 排序时，null 被视为小于任何其他对象。

如果 ArrayList 包含多个具有相同值的元素，该方法只返回其中一个匹配项，并且可能会返回任何一个匹配项，不一定返回第一个。

如果 ArrayList 不包含指定值，该方法将返回负整数。 可以将按位补运算 （~） 应用于此负整数，以获取大于搜索值的第一个元素的索引。 将值插入 ArrayList时，此索引应用作插入点来维护排序顺序。

此方法是 O(log n) 操作，其中 nCount。

另请参阅

• 在集合 中执行 Culture-Insensitive 字符串操作

Source:

ArrayList.cs

Source:

ArrayList.cs

Source:

ArrayList.cs

public:
 virtual int BinarySearch(int index, int count, System::Object ^ value, System::Collections::IComparer ^ comparer);

public virtual int BinarySearch (int index, int count, object value, System.Collections.IComparer comparer);

public virtual int BinarySearch (int index, int count, object? value, System.Collections.IComparer? comparer);

abstract member BinarySearch : int * int * obj * System.Collections.IComparer -> int
override this.BinarySearch : int * int * obj * System.Collections.IComparer -> int

Public Overridable Function BinarySearch (index As Integer, count As Integer, value As Object, comparer As IComparer) As Integer

参数

返回

如果找到 value，则排序 ArrayList中 value 的从零开始的索引;否则为负数，即下一个大于 value 的元素的索引的按位补数;如果没有较大的元素，则为 Count的按位补数。

例外

注解

比较器自定义元素的比较方式。 例如，可以使用 CaseInsensitiveComparer 实例作为比较器来执行不区分大小写的字符串搜索。

如果提供了 comparer，则使用指定的 IComparer 实现将 ArrayList 的元素与指定值进行比较。 ArrayList 的元素必须已根据 comparer定义的排序顺序按递增值进行排序;否则，结果可能不正确。

如果 comparernull，则使用元素本身或指定值提供的 IComparable 实现完成比较。 ArrayList 的元素必须已根据 IComparable 实现定义的排序顺序按递增值进行排序;否则，结果可能不正确。

将 null 与任何类型进行比较，在使用 IComparable时不会生成异常。 排序时，null 被视为小于任何其他对象。

如果 ArrayList 包含多个具有相同值的元素，该方法只返回其中一个匹配项，并且可能会返回任何一个匹配项，不一定返回第一个。

如果 ArrayList 不包含指定值，该方法将返回负整数。 可以将按位补运算 （~） 应用于此负整数，以获取大于搜索值的第一个元素的索引。 将值插入 ArrayList时，此索引应用作插入点来维护排序顺序。

此方法是 O(log n) 操作，其中 ncount。

另请参阅

• IComparer
• IComparable
• 在集合 中执行 Culture-Insensitive 字符串操作