hdu Game of Connections

卡特兰数 递推公式：h(n)=h(n-1)*(4*n-2)/(n+1);

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

 public class Main {

     public static void main(String args[]) {
         Scanner cin = new Scanner(System.in);
         BigInteger[] c = new BigInteger[101];
         c[1] = BigInteger.valueOf(1);
         c[2] = BigInteger.valueOf(2);
         for (int i = 3; i <= 100; i++) {
             BigInteger x1 = BigInteger.valueOf(4*i-2);
             BigInteger x2 = BigInteger.valueOf(i+1);
             c[i]=c[i-1].multiply(x1).divide(x2);
         }

         while (cin.hasNext()) {
             int N = cin.nextInt();
             if (N==-1)
                 break;
             else
                 System.out.println(c[N]);
         }
     }
 }