标签：des style http color java os io strong
Description
| Count the Trees |
Juan is a very gifted programmer, and has a severe case of ACM (he even participated in an ACM world championship a few months ago). Lately, his loved ones are worried about him, because he has found a new exciting problem to exercise his intellectual powers, and he has been speechless for several weeks now. The problem is the determination of the number of different labeled binary trees that can be built using exactly n different elements.
For example, given one element A, just one binary tree can be formed (using A as the root of the tree). With two elements, A and B, four different binary trees can be created, as shown in the figure.
If you are able to provide a solution for this problem, Juan will be able to talk again, and his friends and family will be forever grateful.
1 2 10 25 0
1 4 60949324800 75414671852339208296275849248768000000
题意：卡特兰数
思路：JAVA练手
import java.math.BigInteger;
import java.util.*;
import java.io.*;
/**
* Created by acer on 14-8-7.
*/
public class Main {
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
BigInteger[] catalan = new BigInteger[301], fact = new BigInteger[601];
int n;
fact[0] = BigInteger.ONE;
for (int i = 1; i <= 600; i++)
fact[i] = fact[i-1].multiply(BigInteger.valueOf(i));
for (int i = 0; i <= 300; i++)
catalan[i] = fact[i*2].divide(fact[i+1]).divide(fact[i]);
while ((n = cin.nextInt()) != 0)
System.out.println(catalan[n].multiply(fact[n]));
}
}UVA - 10007 Count the Trees,布布扣,bubuko.com
标签：des style http color java os io strong
原文地址：http://blog.csdn.net/u011345136/article/details/38455801
