public class Ex2
{
    public static void main(String [] args)
    {
        int[] a = {-2, 3, 5, 7, 12};

        System.out.println("sum2(a, 17) " + sum2(a, 17));
        System.out.println("sum2(a, 16) " + sum2(a, 16));

        System.out.println("sum3(a, 17) " + sum3(a, 17));
        System.out.println("sum3(a, 16) " + sum3(a, 16));
    }

    public static boolean sum2 (int[] arr, int num)
    {
        int start = 0;
        int end = arr.length-1;
        while (start < end)
        {
            if (arr[end]+arr[start] > num)
            {
                end--;
            }
            else if (arr[end]+arr[start] < num)
            {
                start++;
            }
            else
            {
                return true;
            }
        }

        return false;
    }

    public static boolean sum3 (int[] arr, int num)
    {
        for (int i=0; i<arr.length; i++)
        {
            int sum = num-arr[i];

            int start = 0;
            int end = arr.length-1;
            while (start < end)
            {
                if (end == i)
                {
                    end--;
                    continue;
                }
                if (start == i)
                {
                    start++;
                    continue;
                }
                else if (arr[end]+arr[start] > sum)
                {
                    end--;
                }
                else if (arr[end]+arr[start] < sum)
                {
                    start++;
                }
                else
                {
                    return true;
                }
            }
        }

        return false;
    }


}