hdu 1023 Train Problem II 卡特兰数 java大数

http://acm.hdu.edu.cn/showproblem.php?pid=1023

//package dhsjdhjkh;

import java.util.*;
import java.io.*;
import java.math.BigInteger;

public class Main {

    
    public static void main(String[] args) 
    {
         int i;
         BigInteger ans [] = new BigInteger[102];
         
         ans[0]= BigInteger.ONE;
         ans[1]= BigInteger.ONE;
         
         for(i=2;i<=100;i++)
             ans[i]=BigInteger.ZERO;
//         h(n)=h(n-1)*(4*n-2)/(n+1);
         for(i=2;i<=100;i++){
             ans[i] = ans[i-1].multiply(BigInteger.valueOf(4*i-2)).divide(BigInteger.valueOf(i+1));
             
         }
             


         Scanner cin = new Scanner(System.in);
         
         while(cin.hasNext())//等价于!=EOF
         {
             int  n = cin.nextInt();//读入一个大整数
             
//
             System.out.println(ans[n]);
             
         }
    
    }

}