Question

Write a Java application that implements the recursive Binary Search alogrithm below:

Write a Java application that implements the recursive Binary Search alogrithm below:/** * Performs the standard binary search using two comparisons * per level. This is a driver that calls the recursive method * @return index where item is found or NOT FOUND if not found */public static <AnyType extends Comparable<? super AnyType>> int binarySearch(AnyType [] a, AnyType x) {return binarySearch(a, x, 0, a.length -1);}/** * Hidden recursive routine. */private static <AnyType extends Comparable<? super AnyType>> int binarySearch(AnyType [] a, AnyType x, int low, int high {if(low > high) return NOT_FOUND; int mid = (low + high)/2; if(a[mid].compareTo(x) < 0) return binarySearch(a, x, mid + 1, high); else if(a[mid].compareTo(x) > 0) return binarySearch(a, x, low, mid - 1); else return mid;}

Answer 1

Hi, Please find my implemetation.

I have also prited trace of execution.

public class BinarySearch {

   public static <AnyType extends Comparable<? super AnyType>>

   int binarySearch(AnyType[] a, AnyType target) {

       return binarySearch(a, target, 0, a.length - 1);

   }

   public static <AnyType extends Comparable<? super AnyType>>

   int binarySearch(AnyType[] a, AnyType target, int min, int max) {

       if (min > max) {

           System.out.println("Min: "+min+", Max: "+max);

           return -1; // target not found

       } else {

           int mid = (min + max) / 2;

           System.out.println("Min: "+min+", Mid: "+mid+", Max: "+max);

           if (a[mid].compareTo(target) < 0) { // too small; go right

               return binarySearch(a, target, mid + 1, max);

           } else if (a[mid].compareTo(target) > 0) { // too large; go left

               return binarySearch(a, target, min, mid - 1);

           } else {

               return mid; // target found; a[mid] == target

           }

       }

   }

   public static void main(String[] args) {

       Integer[] list = {-2, 8, 13, 22, 25, 25, 38, 42, 51, 103};

       System.out.println("Returned Value: "+binarySearch(list, 103, 0, 9));

       System.out.println();

       System.out.println("Returned Value: "+binarySearch(list, 30, 2, 8));

   }

}

/*

Sample run:

Min: 0, Mid: 4, Max: 9

Min: 5, Mid: 7, Max: 9

Min: 8, Mid: 8, Max: 9

Min: 9, Mid: 9, Max: 9

Returned Value: 9

Min: 2, Mid: 5, Max: 8

Min: 6, Mid: 7, Max: 8

Min: 6, Mid: 6, Max: 6

Min: 6, Max: 5

Returned Value: -1

*/