C# | Array.BinarySearch(Array, Int32, Int32, Object, IComparer) Method

Last Updated : 24 Jan, 2019

This method searches for an element which is in a one-dimensional sorted array within a range of elements using a specified IComparer interface.

Syntax:

public static int BinarySearch(Array arr, int index, int length, Object value, IComparer comparer)

Parameters:

arr : The sorted one-dimensional Array which is to be searched.
index : The starting index of the range from which searching will start.
length : The length of the range in which the search will happen.
value : The object to search for.
comparer : When comparing elements then use the IComparer implementation.

Return Value: It returns the index of the specified value in the specified array if the value is found otherwise it returns a negative number. There are different cases of return values as follows:

If the value is not found and value is less than one or more elements in the array, the negative number returned is the bitwise complement of the index of the first element that is larger than value.
If the value is not found and value is greater than all elements in the 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 the value is present in the array.

Below programs illustrate the use of the above-discussed method:

Example 1: In this example the array stores some string value and find some string value after sorting the array.

   // C# program to demonstrate the 
// Array.BinarySearch(Array,  
// Int32, Int32, Object,  
// IComparer) Method 
using System; 
  
class GFG { 
      
// Main Method 
public static void Main() 
{ 
      
    // initializes a new Array 
    string[] arr = new string[5] {"ABCD", 
          "IJKL", "XYZ", "EFGH", "MNOP"}; 
  
    Console.WriteLine("The original Array"); 
      
    // calling "display" function 
    display(arr); 
  
  
    Console.WriteLine("\nsorted array"); 
      
    // sorting the Array 
    Array.Sort(arr); 
    display(arr); 
  
    Console.WriteLine("\n1st call"); 
      
    // search for object "EFGH" 
    object obj1 = "EFGH"; 
      
    // call the "FindObj" function 
    FindObj(arr, obj1); 
  
    Console.WriteLine("\n2nd call"); 
    object obj2 = "ABCD"; 
    FindObj(arr, obj2); 
} 
  
// find object method 
public static void FindObj(string[] Arr, 
                            object Obj) 
{ 
    int index = Array.BinarySearch(Arr, 0, 3,  
         Obj, StringComparer.CurrentCulture); 
           
    if (index < 0)  
    { 
        Console.WriteLine("The object {0} is not "+ 
                    "found\nNext larger object is"+ 
                     " at index {1}", Obj, ~index); 
    } 
      
    else 
    { 
        Console.WriteLine("The object {0} is at"+ 
                       " index {1}", Obj, index); 
    } 
} 
  
// display method 
public static void display(string[] arr) 
{ 
    foreach(string g in arr) 
    { 
        Console.WriteLine(g); 
    } 
} 
} 
 
  

Output:

  The original Array  ABCD  IJKL  XYZ  EFGH  MNOP    sorted array  ABCD  EFGH  IJKL  MNOP  XYZ    1st call  The object EFGH is at index 1    2nd call  The object ABCD is at index 0

Example 2: In this example, here we use “CreateInstance()” method to create a typed array and stores some integer value and search some values after sort the array.

   //C# program to demonstrate the  
// Array.BinarySearch(Array,  
// Int32, Int32, Object,  
// IComparer) Method  
using System; 
  
class GFG 
{ 
      
// Main Method 
public static void Main() 
{ 
    // initializes a new Array. 
    Array arr = Array.CreateInstance(typeof(Int32), 8); 
      
    // Array elements  
    arr.SetValue(20, 0); 
    arr.SetValue(10, 1); 
    arr.SetValue(30, 2); 
    arr.SetValue(40, 3); 
    arr.SetValue(50, 4); 
    arr.SetValue(80, 5); 
    arr.SetValue(70, 6); 
    arr.SetValue(60, 7); 
      
    Console.WriteLine("The original Array"); 
      
    // calling "display" function 
    display(arr); 
  
      
    Console.WriteLine("\nsorted array"); 
      
    // sorting the Array 
    Array.Sort(arr); 
      
    display(arr); 
      
    Console.WriteLine("\n1st call"); 
      
    // search for object 10 
    object obj1 = 10; 
      
    // call the "FindObj" function  
    FindObj(arr, obj1); 
      
    Console.WriteLine("\n2nd call"); 
    object obj2 = 60; 
    FindObj(arr, obj2); 
} 
  
// find object method 
public static void FindObj(Array Arr,  
                         object Obj) 
{ 
    int index = Array.BinarySearch(Arr, 1, 4, 
         Obj, StringComparer.CurrentCulture); 
           
    if (index < 0) 
    { 
        Console.WriteLine("The object {0} is not found\n"+ 
                     "Next larger object is at index {1}",  
                                            Obj, ~index ); 
    } 
    else
    { 
        Console.WriteLine("The object {0} is at "+ 
                        "index {1}", Obj, index ); 
    } 
} 
  
// display method 
public static void display(Array arr) 
{ 
    foreach (int g in arr) 
    { 
        Console.WriteLine(g); 
    } 
} 
} 
 
  

Output:

  The original Array  20  10  30  40  50  80  70  60    sorted array  10  20  30  40  50  60  70  80    1st call  The object 10 is not found  Next larger object is at index 1    2nd call  The object 60 is not found  Next larger object is at index 5

Reference:

https://docs.microsoft.com/en-us/dotnet/api/system.array.binarysearch?view=netframework-4.7.2#System_Array_BinarySearch_System_Array_System_Int32_System_Int32_System_Object_System_Collections_IComparer_

Array.BinarySearch(Array, Object) Method with examples in C#

SoumikMondal

Improve

Article Tags :

C# | Array.BinarySearch(Array, Int32, Int32, Object, IComparer) Method

Similar Reads