POJ 2506 Tiling

Tiling Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 6746   Accepted: 3291 Description In how many ways can you tile a 2xn rectangle by 2x1 or 2x2 tiles?  Here is a sample tiling of a 2x17 rectangle.  Input Input is a sequence of lines, each line containing an integer number 0 <= n <= 250. Output For each line of input, output one integer number in a separate line giving the number of possible tilings of a 2xn rectangle.  Sample Input 2 8 12 100 200 Sample Output 3 171 2731 845100400152152934331135470251 1071292029505993517027974728227441735014801995855195223534251 Source The UofA Local 2000.10.14

 

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();

            if(n==0){

                System.out.println("1");

                continue;

            }else if(n==1){

                System.out.println("1");

                continue;

            }else if(n==2){

                System.out.println("3");

                continue;

            }

                

            BigInteger a=BigInteger.valueOf(1);

            BigInteger b=BigInteger.valueOf(3);

            BigInteger c;

            for(int i=3;i<=n;i++){

                c=b.add(a.multiply(BigInteger.valueOf(2)));

                a=b;

                b=c;

            }

            System.out.println(b);

        }

    }

}