//  Source File:  binsearch.C
//
//  This program demonstrates the iterative
//  version of Binary Search
//
//  Author:  Alan Baumgarten
//  Date:    March 10, 1999


#include <iostream.h>

int BinSearch (int array[], int num_elems, int value);
 
int main() {

    int num[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    int pos;

    pos = BinSearch (num, 10, 3);
    if (pos == -1) {
        cout << "Didn't find 3" << endl;
    } else {
        cout << "Found 3 at position " << pos << endl;
    }

    pos = BinSearch (num, 10, 23);
    if (pos == -1) {
        cout << "Didn't find 23" << endl;
    } else {
        cout << "Found 23 at position " << pos << endl;
    }

    return 0;
}

// This function performs a binary search on 
// an array of integers.  It is assumed that
// the array is sorted in ascending order. 
//
// Parameters:
//    array     - the array to search
//    num_elems - number of elements in the array
//    value     - the value to search for
//
// Returns:
//    If found, the position (index) where found
//    If not found, -1

int BinSearch (int array[], int num_elems, int value) {

    int low = 0, high = num_elems - 1;
    int mid, test;

    while (low <= high) {

        mid = (high + low) / 2;     // midpoint
        test = array[mid];

        if (test == value) {
            return mid;             // found
        } else if (test < value) {
            low = mid + 1;          // look to "right"
        } else {
            high = mid - 1;         // look to "left"
        }
    }
    return -1;      // not found
}