hdu 1131 Count the Trees # java水大数

http://acm.hdu.edu.cn/showproblem.php?pid=1131

求N个不同结点的组成的树的种类

卡特兰数求出 树的结构 的个数，乘以结点的阶乘

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