Array.BinarySearch Method

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

public:
 static int BinarySearch(Array ^ array, System::Object ^ value);

public static int BinarySearch(Array array, object value);

public static int BinarySearch(Array array, object? value);

static member BinarySearch : Array * obj -> int

Public Shared Function BinarySearch (array As Array, value As Object) As Integer

Parameters

Returns

The index of the specified value in the specified array, if value is found; otherwise, a negative number. If value is not found and value is less than one or more elements in array, the negative number returned is the bitwise complement of the index of the first element that is larger than value. If value is not found and value is greater than all elements in array, the negative number returned is the bitwise complement of (the index of the last element plus 1). If this method is called with a non-sorted array, the return value can be incorrect and a negative number could be returned, even if value is present in array.

Exceptions

Examples

The following code example shows how to use BinarySearch to locate a specific object in an Array.

open System

let printValues (myArray: Array) =
    let mutable i = 0
    let cols = myArray.GetLength(myArray.Rank - 1)
    for item in myArray do
        if i < cols then
            i <- i + 1
        else
            printfn ""
            i <- 1;
        printf $"\t{item}"
    printfn ""

let findMyObject (myArr: Array) (myObject: obj) =
    let myIndex = Array.BinarySearch(myArr, myObject)
    if myIndex < 0 then
        printfn $"The object to search for ({myObject}) is not found. The next larger object is at index {~~~myIndex}."
    else
        printfn $"The object to search for ({myObject}) is at index {myIndex}."

// Creates and initializes a new Array.
let myIntArray = [| 8; 2; 6; 3; 7 |]

// Do the required sort first
Array.Sort myIntArray

// Displays the values of the Array.
printfn "The int array contains the following:"
printValues myIntArray

// Locates a specific object that does not exist in the Array.
let myObjectOdd: obj = 1
findMyObject myIntArray myObjectOdd 

// Locates an object that exists in the Array.
let myObjectEven: obj = 6
findMyObject myIntArray myObjectEven
       
// This code produces the following output:
//     The int array contains the following:
//             2       3       6       7       8
//     The object to search for (1) is not found. The next larger object is at index 0.
//     The object to search for (6) is at index 2.

using System;

public class SamplesArray
{
    public static void Main()
    {
        // Creates and initializes a new Array.
        Array myIntArray = Array.CreateInstance(typeof(int), 5);

        myIntArray.SetValue(8, 0);
        myIntArray.SetValue(2, 1);
        myIntArray.SetValue(6, 2);
        myIntArray.SetValue(3, 3);
        myIntArray.SetValue(7, 4);

        // Do the required sort first
        Array.Sort(myIntArray);

        // Displays the values of the Array.
        Console.WriteLine( "The int array contains the following:" );
        PrintValues(myIntArray);

        // Locates a specific object that does not exist in the Array.
        object myObjectOdd = 1;
        FindMyObject( myIntArray, myObjectOdd );

        // Locates an object that exists in the Array.
        object myObjectEven = 6;
        FindMyObject(myIntArray, myObjectEven);
    }

    public static void FindMyObject(Array myArr, object myObject)
    {
        int myIndex=Array.BinarySearch(myArr, 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(Array myArr)
    {
        int i = 0;
        int cols = myArr.GetLength(myArr.Rank - 1);
        foreach (object o in myArr)
        {
            if ( i < cols )
            {
                i++;
            }
            else
            {
                Console.WriteLine();
                i = 1;
            }
            Console.Write( "\t{0}", o);
        }
        Console.WriteLine();
    }
}
// This code produces the following output.
//
//The int array contains the following:
//        2       3       6       7       8
//The object to search for (1) is not found. The next larger object is at index 0
//
//The object to search for (6) is at index 2.

Public Class SamplesArray
    Public Shared Sub Main()
        ' Creates and initializes a new Array.
        Dim myIntArray As Array = Array.CreateInstance( GetType(Int32), 5 )

        myIntArray.SetValue( 8, 0 )
        myIntArray.SetValue( 2, 1 )
        myIntArray.SetValue( 6, 2 )
        myIntArray.SetValue( 3, 3 )
        myIntArray.SetValue( 7, 4 )

        ' Do the required sort first
        Array.Sort(myIntArray)

        ' Displays the values of the Array.
        Console.WriteLine("The Int32 array contains the following:")
        PrintValues(myIntArray)

        ' Locates a specific object that does not exist in the Array.
        Dim myObjectOdd As Object = 1
        FindMyObject(myIntArray, myObjectOdd)

        ' Locates an object that exists in the Array.
        Dim myObjectEven As Object = 6
        FindMyObject(myIntArray, myObjectEven)
    End Sub

    Public Shared Sub FindMyObject(myArr As Array, myObject As Object)
        Dim myIndex As Integer = Array.BinarySearch(myArr, 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(myArr As Array)
        Dim i As Integer = 0
        Dim cols As Integer = myArr.GetLength( myArr.Rank - 1 )
        For Each o As Object In myArr
            If i < cols Then
                i += 1
            Else
                Console.WriteLine()
                i = 1
            End If
            Console.Write( vbTab + "{0}", o)
        Next o
        Console.WriteLine()
    End Sub
End Class
' This code produces the following output.
'
' The Int32 array contains the following:
'         2       3       6       7       8
' The object to search for (1) is not found. The next larger object is at index 0
'
' The object to search for (6) is at index 2.

Remarks

This method does not support searching arrays that contain negative indexes. array must be sorted before calling this method.

If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator (~ in C#, Not in Visual Basic) to the negative result to produce an index. If this index is one greater than the upper bound of the array, there are no elements larger than value in the array. Otherwise, it is the index of the first element that is larger than value.

Either value or every element of array must implement the IComparable interface, which is used for comparisons. The elements of array must already be sorted in increasing value according to the sort order defined by the IComparable implementation; otherwise, the result might be incorrect.

Duplicate elements are allowed. If the Array contains more than one element equal to value, the method returns the index of only one of the occurrences, and not necessarily the first one.

null can always be compared with any other reference type; therefore, comparisons with null do not generate an exception.

This method is an O(log n) operation, where n is the Length of array.

See also

• IComparable
• Sort
• Performing Culture-Insensitive String Operations in Arrays

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

public:
 static int BinarySearch(Array ^ array, System::Object ^ value, System::Collections::IComparer ^ comparer);

public static int BinarySearch(Array array, object value, System.Collections.IComparer comparer);

public static int BinarySearch(Array array, object? value, System.Collections.IComparer? comparer);

static member BinarySearch : Array * obj * System.Collections.IComparer -> int

Public Shared Function BinarySearch (array As Array, value As Object, comparer As IComparer) As Integer

Parameters

Returns

The index of the specified value in the specified array, if value is found; otherwise, a negative number. If value is not found and value is less than one or more elements in array, the negative number returned is the bitwise complement of the index of the first element that is larger than value. If value is not found and value is greater than all elements in array, the negative number returned is the bitwise complement of (the index of the last element plus 1). If this method is called with a non-sorted array, the return value can be incorrect and a negative number could be returned, even if value is present in array.

Exceptions

Remarks

This method does not support searching arrays that contain negative indexes. array must be sorted before calling this method.

If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator (~ in C#, Not in Visual Basic) to the negative result to produce an index. If this index is one greater than the upper bound of the array, there are no elements larger than value in the array. Otherwise, it is the index of the first element that is larger than value.

The comparer customizes how the elements are compared. For example, you can use a System.Collections.CaseInsensitiveComparer as the comparer to perform case-insensitive string searches.

If comparer is not null, the elements of array are compared to the specified value using the specified IComparer implementation. The elements of array must already be sorted in increasing value according to the sort order defined by comparer; otherwise, the result might be incorrect.

Ifcomparer is null, the comparison is done using the IComparable implementation provided by the element itself or by the specified value. The elements of array must already be sorted in increasing value according to the sort order defined by the IComparable implementation; otherwise, the result might be incorrect.

Duplicate elements are allowed. If the Array contains more than one element equal to value, the method returns the index of only one of the occurrences, and not necessarily the first one.

null can always be compared with any other reference type; therefore, comparisons with null do not generate an exception.

This method is an O(log n) operation, where n is the Length of array.

See also

• IComparer
• IComparable
• Sort
• Performing Culture-Insensitive String Operations in Arrays

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

Source:

Array.cs

public:
 static int BinarySearch(Array ^ array, int index, int length, System::Object ^ value);

public static int BinarySearch(Array array, int index, int length, object value);

public static int BinarySearch(Array array, int index, int length, object? value);

static member BinarySearch : Array * int * int * obj -> int

Public Shared Function BinarySearch (array As Array, index As Integer, length As Integer, value As Object) As Integer

Parameters

Returns

The index of the specified value in the specified array, if value is found; otherwise, a negative number. If value is not found and value is less than one or more elements in array, the negative number returned is the bitwise complement of the index of the first element that is larger than value. If value is not found and value is greater than all elements in array, the negative number returned is the bitwise complement of (the index of the last element plus 1). If this method is called with a non-sorted array, the return value can be incorrect and a negative number could be returned, even if value is present in array.

Exceptions

Remarks

This method does not support searching arrays that contain negative indexes. array must be sorted before calling this method.

If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator (~ in C#, Not in Visual Basic) to the negative result to produce an index. If this index is one greater than the upper bound of the array, there are no elements larger than value in the array. Otherwise, it is the index of the first element that is larger than value.

Either value or every element of array must implement the IComparable interface, whi