//  Source File:  binsearch2.C
//
//  This program demonstrates the recursive
//  version of Binary Search
//
//  Author:  Alan Baumgarten
//  Date:    March 10, 1999

#include <iostream.h>

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

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

    pos = BinSearch (num, 0, 9, 3);
    if (pos == -1) {
        cout << "Didn't find 3" << endl;
    } else {
        cout << "Found 3 at position " << pos << endl;
    }

    pos = BinSearch (num, 0, 9, 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
//    low   - lower index of range of array to search
//    high  - higher index of range of array to search
//    value - the value to search for
//
// Returns:
//    If found, the position (index) where found
//    If not found, -1

int BinSearch (int array[], int low, int high, int value) {

    int mid, test;

    if (low > high) {           // not found
        return -1;
    }

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

    if (test == value) {
        return mid;             // found
    } else if (test < value) {
        return BinSearch (array, mid + 1, high, value);
    } else {
        return BinSearch (array, low, mid - 1, value);
    }
}