poj2084 Game of Connections

Catalan数，组合数学书上有公式。

import java.math.*;  import java.io.*;  import java.util.*;  public class Main {      public static void main(String [] args){          Scanner cin = new Scanner(System.in);          BigInteger a[] = new BigInteger[101];          a[0] = BigInteger.ONE;          for(int i=1; i<=100; ++i){              a[i] = a[i-1].multiply(BigInteger.valueOf(4*i-2)).divide(BigInteger.valueOf(i+1));          }          while(cin.hasNext()){          int n= cin.nextInt();        if(n==-1) break;            System.out.println(a[n]);          }      }  }