public static void main(String[] args)
{
    var array = new[] { 17, 25, 77, 11, 24, 47, 73, 18 };
    QuickSort(array, 0, array.Length - 2, array.Length - 1);
}

public static void QuickSort(int[] array, int start, int end, int pivot)
{
    if (start >= end) return;

    int leftScan = start;
    int rightScan = end;

    bool scannersMet = false;

    while (!scannersMet)
    {
        while (array[leftScan] < array[pivot])
        {
            leftScan++;
        }

        while (array[pivot] < array[rightScan])
        {
            rightScan--;
        }

        if (leftScan + 1 >= rightScan)
        {
            scannersMet = true;
        }
        else
        {
            int temp1 = array[leftScan];
            array[leftScan] = array[rightScan];
            array[rightScan] = temp1;
        }
    }

    int temp2 = array[pivot];
    array[pivot] = array[leftScan];
    array[leftScan] = temp2;

    QuickSort(array, start, leftScan - 1, leftScan - 1);

    QuickSort(array, leftScan + 1, end, end);
}