binary search

[just4444]

Hey new to programming and trying to work out how to print the position of the input int within the array.

  void swap(int& a, int& b)
{
	int temp = a;
	a = b;							
	b = temp;
}

void BubbleSort(int array[], int n)
{
	if (n < 2)      
		return;
	bool sorted = false;
	while (!sorted)
	{
		sorted = true;
		for (int i = 0; i < n - 1; ++i)
		{
			if (array[i] < array[i + 1]) {
				swap(array[i], array[i + 1]);
				sorted = false;
			}
		}
	}
}
int binary_search(int array[], int start_index, int end_index, int key)
{
	while (start_index <= end_index)
	{
		int pivot = (start_index + end_index) / 2;
		
		if (array[pivot] == key)
			return pivot;
		if (key < array[pivot])
			end_index = pivot - 1;
		else
			start_index = pivot + 1;
	}
	return -1;
}
int main()
{
	const int array_size = 25;
	int array_to_be_sorted[array_size] =

	{
		14,65,63,1,54,
		89,84,9,98,57,
		71,18,21,84,69,
		28,11,83,13,42,
		64,58,78,82,13
	};

	BubbleSort(array_to_be_sorted, array_size);

	while (true)
	{

		cout << endl << "Enter a number to find in the sequence: -1 to end" << endl;
		int key_search = -1;
		cin >> key_search;
		cin.ignore(numeric_limits<streamsize>::max(), '\n');
		if (key_search == -1)

			break;

		int binary_search(int array[], int start_index, int end_index, int key);
		
		// if binaray_searh ==  -1 "Couldn't find " << keysearch << " in the list" << endl; 
		//else cout "found" "<< keysearch>>"  "at position" "<<_>>" endl;
	}		
}

[salem c]

> BubbleSort(array_to_be_sorted, array_size);
This is a function call.

> int binary_search(int array[], int start_index, int end_index, int key);
This isn't a function call. It's a function prototype.

[just4444]

im still going wrong somewhere and cant seem to work out where. Im getting it to go through and it prints out the "couldn't find <<whatever key was pressed>> in the list" but the number im using is in the array to be sorted list.

any more help would be amazing

while (true)
{

cout << endl << "Enter a number to find in the sequence: -1 to end" << endl;
int key_search = -1;
cin >> key_search;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
if (key_search == -1)

break;
{
int r = binary_search(array_to_be_sorted, 0, array_size - 1, key_search);

if (r == -1)
cout << "Couldn't find " << key_search << " in the list" << endl;
else
cout << "Found " << key_search << " at position " << r << endl;

}
return 0;
}
}

[salem c]

I would suggest (as a debug) printing out the array after you've sorted it, to actually verify that it's sorted.

As a separate debug, you could try this.

int test[] = { 1, 2, 3 };
int r1 = binary_search(test, 0, 2, 2);  // should find this
int r2 = binary_search(test, 0, 2, 99); // shouldn't find this
cout << "r1=" << r1 << endl;
cout << "r2=" << r2 << endl;

[just4444]

Thanks. worked out I was sorting the numbers descending rather then ascending