Binary search Program in java With Explanation Using Different Ways

 Binary search Program in java

import java.util.Scanner; class BinarySearch { public static void main(String args[]) { int c, first, last, middle, n, search, array[]; Scanner in = new Scanner(System.in); System.out.println("Enter number of elements"); n = in.nextInt(); array = new int[n]; System.out.println("Enter " + n + " integers"); for (c = 0; c < n; c++) array[c] = in.nextInt(); System.out.println("Enter value to find"); search = in.nextInt(); first = 0; last = n - 1; middle = (first + last)/2; while( first <= last ) { if ( array[middle] < search ) first = middle + 1; else if ( array[middle] == search ) { System.out.println(search + " found at location " + (middle + 1) + "."); break; } else last = middle - 1; middle = (first + last)/2; } if ( first > last ) System.out.println(search + " is not present in the list.\n"); } }

public class BinarySearch { public static int binarySearch(int arr[], int x) { int left = 0, right = arr.length - 1; while (left <= right) { int mid = left + (right - left) / 2; if (arr[mid] == x) { return mid; } if (arr[mid] < x) { left = mid + 1; } else { right = mid - 1; } } return -1; } public static void main(String args[]) { int arr[] = { 2, 3, 4, 10, 40 }; int x = 10; int result = binarySearch(arr, x); if (result == -1) { System.out.println("Element not present"); } else { System.out.println("Element found at index " + result); } } }

Explanation:

• The function binarySearch takes an integer array arr and an integer x as input and returns the index of x in arr if it is present. If not, it returns -1.
• The variables left and right are initialized to 0 and arr.length-1, respectively, to represent the lower and upper bounds of the search space.
• In each iteration of the while loop, mid is calculated as the average of left and right.
• If arr[mid] is equal to x, the function returns mid.
• If arr[mid] is less than x, the search space is updated to the right of mid by setting left to mid + 1.
• If arr[mid] is greater than x, the search space is updated to the left of mid by setting right to mid - 1.
• The while loop continues until left is greater than right or x is found. If x is not found, the function returns -1.
• In the main method, the array arr and the search value x are defined, and the result of the binarySearch function is stored in result.
• If result is -1, the program outputs that the element is not present. Otherwise, it outputs the index at which the element was found.
  

Recursive Binary Search Algorithm in Java

 

public int binarySearch(int arr[], int l, int r, int x) { if (r >= l) { int mid = l + (r - l) / 2; if (arr[mid] == x) return mid; if (arr[mid] > x) return binarySearch(arr, l, mid - 1, x); return binarySearch(arr, mid + 1, r, x); } return -1; }

 

 Java Stream Binary Search Algorithm

 

public int binarySearch(int arr[], int x) { return IntStream.of(arr).boxed().sorted().collect(Collectors.toList()).indexOf(x); }

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