The 7th Blue Bridge Cup Java Group A Final Exam Questions

1. Factorial


The factorial of the number 9 is equal to: 362880
Its binary representation is: 1011000100110000000
This number has a total of 19 bits.


Please calculate, how many bits are there in the binary representation of the factorial of 9999?


Note: What needs to be submitted is an integer, do not fill in any irrelevant content (such as explanation, etc.)

Answer: 118445

Idea: Examine BigInteger

import java.util. *;
import java.math.*;
public class Main {

    public static void main(String[] args) {
        // write your code here
        BigInteger num;
        num=BigInteger.ONE;
        for(int i=1;i<=9999;i++)
        {
            BigInteger temp=BigInteger.valueOf(i);
            num=num.multiply(temp);
        }
        String str=num.toString(2);
        System.out.println(str.length());
    }

}