【HDU】1250 - Hat's Fibonacci（java - BigDecimal）

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Hat's Fibonacci

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 10562 Accepted Submission(s): 3502

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

用BigDecimal打表。

代码如下：

import java.math.BigDecimal;
import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
	    BigDecimal f[] = new BigDecimal [10011];
	    f[1] = f[2] = f[3] = f[4] = new BigDecimal(1);
	    for (int i = 5 ; i <= 10000 ; i++)
	    {
	        f[i] = f[i-1].add ( f[i-2].add ( f[i-3].add ( f[i-4] )));
	    }
		Scanner sc = new Scanner(System.in);
		while (sc.hasNext())
		{
			int n = sc.nextInt();
			System.out.println(f[n]);
		}
	}
}