2018 ICPC 焦作 E [大數+ 數論]

熟悉一下大數的板子

import java.util.Scanner;
import java.math.*;
public class Main {
	public static int [] prime = new int [5001];
	public static int [] isprime = new int [5001];
	public static int tot = 0;
	public static void getprime()
	{
		isprime[1] = 0;
		for(int i=2;i<=5000;i++) isprime[i] = 1;
		for(int i=2;i<=5000;i++)
		{
			if(isprime[i]==0) continue;
			//System.out.println(i);
			prime[++tot] = i;
			for(int j=i*2;j<=5000;j+=i) isprime[j] = 0;
		}
	}
	public static void main(String[] args) {
		getprime();
		Scanner in = new Scanner(System.in);
		int t = in.nextInt();
		//for(int i=1;i<=tot;i++) System.out.println(prime[i]);
		while(t--!=0)
		{
			tot = 0;
			BigInteger n = in.nextBigInteger();
			BigInteger res = BigInteger.ONE;
			BigInteger sum = BigInteger.ONE;
			for(int i=1;i<=70;i++)
			{
				if(res.multiply(BigInteger.valueOf(prime[i])).compareTo(n)<=0)
				{
					
					res = res.multiply(BigInteger.valueOf(prime[i]));
					sum = sum.multiply(BigInteger.valueOf(prime[i]+1));
				}
				else break;
			}
			//System.out.println(res+" "+sum);
			
			BigInteger g =sum.gcd(res);
			sum  = sum.divide(g);
			res = res.divide(g);
			System.out.println(res+"/"+sum);
			
		}
	}
	
}