hdu1250(Java）大数相加的问题

Hat's Fibonacci

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 10525 Accepted Submission(s):
3483

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

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

public class Main1250{
public static void main(String args[]){
Scanner cin=new Scanner(System.in);
BigDecimal []a=new BigDecimal[10007];
a[0]=new BigDecimal(1);
a[1]=new BigDecimal(1);
a[2]=new BigDecimal(1);
a[3]=new BigDecimal(1);
for(int i=4;i<10007;i++)
a[i]=a[i-1].add(a[i-2]).add(a[i-3]).add(a[i-4]);
while(cin.hasNext()){
int n=cin.nextInt();
System.out.println(a[n-1]);

}
}
}

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

 

这个地方要注意数组要开大点，题目不是说只有2005个数