hdu 2067 小兔的棋盘 卡特兰数+java

根据规则可以看出来就是n的卡特兰数乘二

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

public class Main{

    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        int n=0,i=0,cas=0;
        BigInteger[] a=new BigInteger[50];
        a[0]=BigInteger.ONE;
        for(i=1;i<=36;i++)
        {
            a[i]=a[i-1].multiply(BigInteger.valueOf(4*i-2)).divide(BigInteger.valueOf(i+1));
            a[i-1]=a[i-1].multiply(BigInteger.valueOf(2));
        }
        while(in.hasNextInt())
        {
            n=in.nextInt();
            if(n==-1) break;
            cas++;
            System.out.print(cas+" "+n+" ");
            System.out.println(a[n]);
        }
        in.close();
    }

}