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Java

Posted by Diego Murray
Diego Murray
2,515 Points

Euler 20 - Sum digits in 100! ( JAVA )

Can't seem to debug the following code. I believe the factorial method is correct. There must be an error somewhere in between converting it to a String and then adding up the individual characters.

Please add any extra recommendations on how to make the code more legible or perhaps faster.

Thanks

package euler20;

import java.math.BigInteger;

public class sumDigitsIn100Factorial {


        public static final int n = 100;

        public static void main(String[] args) {

            long startTime = System.currentTimeMillis();

            System.out.println("100! = " + factorial(n));
            System.out.println("Sum of all digits in 100! = " + sumOfDigits(factorial(n)));

            long endTime = System.currentTimeMillis();
            System.out.println("Time: " + (endTime - startTime) + " ms");

        }

        public static BigInteger factorial(int n1) {

            BigInteger n = BigInteger.ONE;

            for (int i = 1; i <= n1; i++) {
                n = n.multiply(BigInteger.valueOf(i));
            }
            return n;
        }

        public static int sumOfDigits(BigInteger n1) {

            String bigIntStr = factorial(n).toString();
            int sum = 0;

            for (int i = 1; i <= bigIntStr.length(); i++) {
                sum += Integer.parseInt(String.valueOf(i));
            }
            return sum;
        }
}