Rupsa and the Game: What's wrong with this code?

general
1

import java.math.BigInteger;
import java.util.Scanner;
class Wandbox
{
----public static void main(String[] args)
----{
--------Scanner sc = new Scanner(System.in);
--------BigInteger T = sc.nextBigInteger();
--------BigInteger dos = new BigInteger(“2”);
--------BigInteger modulo = new BigInteger(“1000000007”);
--------for (BigInteger bi = T; bi.compareTo(BigInteger.ZERO) > 0; bi = bi.subtract(BigInteger.ONE)) {
------------BigInteger N = sc.nextBigInteger(); BigInteger ant = new BigInteger(“0”); BigInteger suma = new BigInteger(“0”);
------------for (BigInteger bii = N; bii.compareTo(BigInteger.ZERO) > -1; bii = bii.subtract(BigInteger.ONE)){
----------------BigInteger E = sc.nextBigInteger();
----------------BigInteger multi = E.multiply(ant);
----------------BigInteger sum = E.add(ant);
----------------ant = multi.add(sum);
----------------suma = suma.add(E);
------------}
------------ant = ant.subtract(suma);
------------ant = ant.multiply(dos);
------------ant = ant.mod(modulo);
------------System.out.println(ant);
--------}
----}
}

2

You dont have to use big integer if you use modulo properly. Give a read to fast exponentiation, or perhaps try storing (power of 2)%mod in array and use it there after.

That, assuming you have got approach correct, its hard to tell your approach without comments.

3

Yeah, my approach was incorrect that was the problem.