http://acm.hdu.edu.cn/showproblem.php?pid=1023&&卡特兰数

Problem Description

As we all know the Train Problem I, the boss of the Ignatius Train Station want to know if all the trains come in strict-increasing order, how many orders that all the trains can get out of the railway.

Input

The input contains several test cases. Each test cases consists of a number N(1<=N<=100). The input is terminated by the end of file.

Output

For each test case, you should output how many ways that all the trains can get out of the railway.

Sample Input

  

   1
2
3
10
  

Sample Output

  

   1
2
5
16796

  
  

   java写的。。。。
  
  

   AC代码：
   http://blog.youkuaiyun.com/smallacmer/article/details/7770855
  
  

   
import java.util.*;
import java.math.BigInteger;
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO 自动生成方法存根
		BigInteger num[]=new BigInteger[105];
		num[1]=BigInteger.ONE;
		num[2]=BigInteger.valueOf(2);
		num[3]=BigInteger.valueOf(5);
		for(int i=4;i<105;i++)
			{
			BigInteger b=BigInteger.valueOf(4);
			b= b.multiply(BigInteger.valueOf(i)).subtract(BigInteger.valueOf(2));
            num[i]=num[i-1].multiply(b).divide(BigInteger.valueOf(i+1));
			}

		Scanner cin=new Scanner(System.in);
		int n;
		while(cin.hasNext())
		{
			n=cin.nextInt();
			System.out.println(num[n]);
		}
	}

}