help with binary search

Code:

#include <iostream>
using namespace std;

int search(long array[], int size, long value);

int main()
{
	long nums[] = {5658845, 8080152, 1005231,
                   4520125, 4562555, 6545231,
                   7895122, 5552012, 3852085,
                   8777541, 5050552, 7576651,
                   8451277, 7825877, 7881200,
                   1302850, 1250255, 4581002};
	
	long number;
	
	int  results;

	cout << "Enter a charge account number" << endl;
	cin  >> number;

	while (results = search(nums, 18, number) == -1)
	{
		cin.clear();
		cin.ignore(INT_MAX, '\n');

		cout << "Invalid entry" << endl;
		cout << "Re-enter" << endl;
		cin  >> number;
	}

	cout << "Your number is valid" << endl;

	return 0;
}

int search(long array[], int size, long value)
{
	int first = 0;
	int middle;
	int last  = size - 1;

    int position = -1;
	int found    = 0;

	while (!found && first <= last)
	{
		middle = (first + last) / 2;

		if (array[middle] == value)
		{
			found    = 1;
			position = middle;
		}

		else if (array[middle] > value)
			last  = middle - 1;

		else
			first = middle = 1;
	}

	return position;
}

For some reason, only 8777541, 4562555, and 3852085 are considered valid numbers. All of the other numbers are consider invalid or cause some kind of weird error.


Never mind. I realize that the numbers have to be sorted in order for a binary search to work.

When I used a sorting algorithm, some numbers were still causing problems (like 7895122).

Code:

#include <iostream>
using namespace std;

int  search(long array[], int size, long value);

void sort              (long array[], int size);

int main()
{
	long nums[] = {5658845, 8080152, 1005231,
                   4520125, 4562555, 6545231,
                   7895122, 5552012, 3852085,
                   8777541, 5050552, 7576651,
                   8451277, 7825877, 7881200,
                   1302850, 1250255, 4581002};
	long number;

	int  results;

	sort(nums, 18);

	cout << "Enter a charge account number" << endl;
	cin  >> number;

	while ((results = search(nums, 18, number)) == -1)
	{
		cin.clear();
		cin.ignore(INT_MAX, '\n');

		cout << "Invalid entry" << endl;
		cout << "Re-enter" << endl;
		cin  >> number;
	}

		cout << "Your number is valid" << endl;

	return 0;
}

int search(long array[], int size, long value)
{
	int first = 0;
	int middle;
	int last  = size - 1;

    int position = -1;
	int found    = 0;

	while (!found && first <= last)
	{
		middle = (first + last) / 2;

		if (array[middle] == value)
		{
			found    = 1;
			position = middle;
		}

		else if (array[middle] > value)
			last  = middle - 1;

		else
			first = middle = 1;
	}	

	return position;
}

void sort(long array[], int size)
{
	long hold;
	int  finish;

	do
	{
		finish = 0;
		
		for (int i = 0; i < size - 1; i++)
		{
			if (array[i] > array[i + 1])
			{
				hold         = array[i];
				array[i]     = array[i + 1];
				array[i + 1] = hold;

				finish = 1;
			}
		}
	}while (finish != 0);
}

Could my compiler be a little faulty, or is there really something wrong with that code?

>>else
>>first = middle = 1;
A little typo in that one, eh?