hdu 1023

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

卡特兰数问题

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