hdu 1250(大整数)

Hat's Fibonacci

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 10430    Accepted Submission(s): 3447

Problem Description

A Fibonacci sequence is calculated by adding the previous two members the sequence, with the first two members being both 1.
F(1) = 1, F(2) = 1, F(3) = 1,F(4) = 1, F(n>4) = F(n - 1) + F(n-2) + F(n-3) + F(n-4)
Your task is to take a number as input, and print that Fibonacci number.

 

Input

Each line will contain an integers. Process to end of file.

 

Output

For each case, output the result in a line.

 

Sample Input

100

 

Sample Output

4203968145672990846840663646 Note: No generated Fibonacci number in excess of 2005 digits will be in the test data, ie. F(20) = 66526 has 5 digits.

 

2005位的数大概在7100左右

import java.math.BigInteger;
import java.util.Scanner;


 
public class Main {
    
    public static void main(String[] args) {
        BigInteger [] b = new BigInteger[7200];
        b[1]=b[2]=b[3]=b[4]= BigInteger.valueOf(1);
        int len = 0;
        for(int i=5;i<7200;i++){
            b[i] = b[i-1].add(b[i-2]).add(b[i-3]).add(b[i-4]);
        }
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int n = sc.nextInt();
            System.out.println(b[n]);
        }
    }
}