// Faan Tone Liu  , demo program for comp 1672, winter 2003
// Binary search function and insert sort function, and testing it

#include <iostream>
#include <fstream>

using namespace std;
int binarySearch(const int b[], int searchkey, int size);
void insert_sort(int a[], int len);

// read elements of an array in from a file.  Sort them.
// Get search key from user, search for it in array.
int main()
{
    const int maxarrlen(100);
    const int maxnamelen(80);
    char filename[maxnamelen];
    ifstream listfile;
    int arr[maxarrlen];
    int numelements(0);
    int key, result;

    cout << "Enter file name containing list (no more than 100 elements): ";
    cin >> filename;
    listfile.open(filename, ios::in);   // open input file
	if (!listfile.is_open()) {
            cout << "Unable to open file." << endl;
            return 1;
	}

    // read the list from the file into the array
    while (listfile >> arr[numelements])
        numelements = numelements + 1;

    //sort it
    insert_sort(arr, numelements);

    cout << "What number are you looking for? ";
    cin >> key;
    result = binarySearch(arr, key, numelements);
    if (result < 0)
        cout << "The number was not found in the list" << endl;
    else 
       	cout << "The number " << key << " was found at position " << result <<
            " of the array." << endl;
    return 0;
}
							  
//Search through array b which contains size elements to locate the
// index of searchkey, a value we hope to find in b.  If it is
// not found, return -1
int binarySearch(const int b[], int searchkey, int size)
{
    int low, middle, high;

    low = 0;
    high = size-1;
    while (low <= high) {
        middle = (low+high)/2;
        if (searchkey == b[middle])      // found it!
            return middle;
        else if (searchkey < b[middle])  // it's in the lower half
            high = middle -1;
        else
            low = middle + 1;
    }

    return -1;
}

// sort the array a in increasing order
// use an insert sort algorithm.  This is an inefficient algorithm!
// You should use merge sort or quick sort instead
void insert_sort(int a[], int len)
{
    int BadOrder, temp, location;
    // Traverse the list - checking for correct ordering
    for (BadOrder = 1; BadOrder < len; BadOrder++) {
        if (a[BadOrder] < a[BadOrder-1]) {
            // this one's in the wrong place!
            temp = a[BadOrder];    // remember what this element is
            location = BadOrder;   // these next few lines slides elements
            do {                   // down to make room for this one
                a[location] = a[location-1];
                location--;
            } while (location>0 && a[location-1] > temp);
            a[location] = temp;    // Put out-of-order number in the right place
        }
    }
}