Program on binary selection>>>

#include<iostream.h>

#include<conio.h>

void main()

{

    clrscr();

    int arr[20];    //Array to be searched

    int n;      //Number of elements in the array

    int i;

    // Get the number of elements to store in the array

    while (1)

    {

cout << "Enter the number of elements in the array: ";

cin >> n;

if ((n>0) && (n <= 20))

   break;

else

   cout << "\nArray should have minimum 1 and maximum 20 elements.\n\n";

    }

    //Accept array elements

    cout << "\n---------------------------------------\n";

    cout << " Enter array elements in ascending order\n";

    cout << "----------------------------------------\n";

    for (i = 0; i < n; i++)

    {

cout << "<" << (i + 1) << "> ";

cin >> arr[i];

    }

    char ch;

    do

    {

//Accept the number to be searched

int item;

cout << "\nEnter the element you want to search: ";

cin >> item;

//Apply binary search

int lowerbound = 0;

int upperbound = n - 1;

//Obtain the index of the middlemost element

int mid = (lowerbound + upperbound) / 2;

int ctr = 1;

while ((item != arr[mid]) && (lowerbound <= upperbound))

{

   if (item > arr[mid])

lowerbound = mid + 1;

   else

upperbound = mid - 1;

   mid = (lowerbound + upperbound) / 2;

   ctr++;

}

if (item == arr[mid])

   cout << "\n" << item << " found at position " << (mid+1) << endl;

else

   cout << "\n" << item << " not found in the array" << endl;

cout<<"\nNumber of comparisons: " <<ctr;

cout << "\n\nContinue search (y/n):";

cin >> ch;

    } while ((ch == 'y') || (ch == 'Y'));

}