Java大数加法 HDU1002 HDU1250

import java.math.*;
import java.util.Scanner;


public class Main{
    public static void main(String[] args){
        BigInteger a,b;
        int n;
        BigInteger ans;
        Scanner cin = new Scanner(System.in);
        n=cin.nextInt();
        a=cin.nextBigInteger();
        b=cin.nextBigInteger();
        ans=a.add(b);
        System.out.println("Case 1:");
        System.out.println(a+" + "+b+" = "+ans);
        for(int i=2;i<=n;i++)
        {
            a=cin.nextBigInteger();
            b=cin.nextBigInteger();
            ans=a.add(b);
            System.out.println();
            System.out.println("Case "+i+":");
            System.out.println(a+" + "+b+" = "+ans);
        }
    }
}

import java.math.*;
import java.util.*;

public class Main
{
    static BigInteger arr[] = new BigInteger [1000000];
    public static void main(String[] args)
    {
        Scanner cin=new Scanner(System.in);
        int n;
        while(cin.hasNext())
        {
            n=cin.nextInt();
            arr[1]=arr[2]=arr[3]=arr[4]=BigInteger.ONE;
            for(int i=5;i<=n;i++)
            {
                arr[i]=BigInteger.ZERO;    
                arr[i]=arr[i].add(arr[i-1]);
                arr[i]=arr[i].add(arr[i-2]);
                arr[i]=arr[i].add(arr[i-3]);
                arr[i]=arr[i].add(arr[i-4]);
            }
            System.out.println(arr[n]);
        }
    }
}