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): 5640    Accepted Submission(s): 1873

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

4203968145672990846840663646Note: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

代码：

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

public class Main {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  Scanner input=new Scanner(System.in);
  while(input.hasNext()){
   int n=input.nextInt();
   if(n==1||n==2||n==3||n==4){
    System.out.println(1);
   }
   else
   {
       BigInteger a=BigInteger.valueOf(1);
       BigInteger b=BigInteger.valueOf(1);
       BigInteger c=BigInteger.valueOf(1);
       BigInteger d=BigInteger.valueOf(1);
       BigInteger num=BigInteger.valueOf(0);
    for(int i=5;i<=n;i++)
    {
     num=a.add(b).add(c).add(d);
     a=b;
     b=c;
     c=d;
     d=num;
    }
    System.out.println(num);
   }
  }
  
 }

}