HDU 1250 Hat's Fibonacci

Hat's Fibonacci

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 4547    Accepted Submission(s): 1544

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.

 

Author

戴帽子的

 

Recommend

Ignatius.L

 

 

 

 

 

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

public class Main{
    public static void main(String[] args){
        Scanner cin = new Scanner(System.in);
        int n;
        while(cin.hasNext()){
            n = cin.nextInt();
            BigInteger a = BigInteger.valueOf(1);
            BigInteger b = BigInteger.valueOf(1);
            BigInteger c = BigInteger.valueOf(1);
            BigInteger d = BigInteger.valueOf(1);
            BigInteger e = BigInteger.valueOf(1);
            for(int i=5; i<=n; i++){
                e = a.add(b.add(c.add(d)));
                a = b;
                b = c;
                c = d;
                d = e;
            }
            System.out.println(e);
        }
    }
}