hdu-1023-Train Problem II

Train Problem II

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 5752    Accepted Submission(s): 3115

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

卡特兰数的应用

import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
	Scanner in=new Scanner(System.in);
	BigDecimal[] a=new BigDecimal[105];
	BigDecimal b,c,d,e;
	a[1]=new BigDecimal(1);
	for(int i=2;i<101;i++)
	{
		b=new BigDecimal(4*i-2);
		c=new BigDecimal(i+1);
		d=a[i-1].multiply(b);
		a[i]=d.divide(c);
	}
	while(in.hasNext())
	{
		int x=in.nextInt();
		System.out.println(a[x]);
	}
	}
}