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Binary Search Programs

Basic Overview Of Binary Search:

  • A binary search algorithm finds the position of a specified input value within an array sorted by key value.
  • For binary search, the array should be sorted i.e. arranged in ascending or descending order.
  • In Binary search, the search key value with the key value of the middle element of the array. If the key element match, then a matching element has been found and its position, is returned.
  • if the search key is less than the middle element's key, then the algorithm repeats its action on the sub-array to the left of the middle element or, if the search key is greater, on the sub-array to the right.
  • If the remaining array to be searched is empty, then the key cannot be found in the array and a “key is not found” message returned.

Eclipse Programs

Steps :

Create new java class as follows.
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Write the code for binary search algorithm as follows


import java.util.Scanner;

public class BinarySearchImpl {
	   public static void main(String args[])
	      int counter, numberOfElements, key, array[], first, last, middle;
	      //To get the user input
	      Scanner input = new Scanner(;
	      System.out.println("Enter total number of elements :");
	      numberOfElements = input.nextInt(); 

	      //Creating array to store the numbers of size n
	      array = new int[numberOfElements];

	      System.out.println("Enter " + numberOfElements + " integers");
	      //Loop to store each entered number in array
	      for (counter = 0; counter < numberOfElements; counter++)
	          array[counter] = input.nextInt();

	      System.out.println("Enter key value to find :");
	      key = input.nextInt();
	      first = 0;
	      last = numberOfElements;
	      middle = (first + last)/2;

	      while( first <= last )
	         if ( array[middle] < key )
	           first = middle + 1;
	         else if ( array[middle] == key )
	           System.out.println(key + " found at location " + (middle + 1) + ".");
	             last = middle - 1;
	         middle = (first + last)/2;
	      if ( first > last )
	          System.out.println(key + " is not found.\n");

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  • Now run the programs as Java Application
  • Enter the total number of elements on console
  • Enter the number to be searched and the key will be searched.

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