HDU 1130

题目大意

给定节点数 ， 求通过这么多个节点能得到的二叉树的组成方式

用卡特兰数解决

f[n] = (4*n-2) * f[n-1] / (n+1);

递归不断解决

/**
 * @(#)Main.java
 *
 *
 * @author 
 * @version 1.00 2014/12/29
 */

import java.util.Scanner;
import java.math.*;

public class Main {

    
    public static void main(String [] args){
        int n;
        Scanner input = new Scanner(System.in);

        while(input.hasNext()){
            n = input.nextInt();
            BigInteger cur = BigInteger.valueOf(1);
            for(int i = 2 ; i<=n ; i++){
                int t1 = 4*i - 2;
                int t2 = i+1;
                BigInteger tmp1 = BigInteger.valueOf(t1);
                cur = cur.multiply(tmp1);
                BigInteger tmp2 = BigInteger.valueOf(t2);
                cur = cur.divide(tmp2);
            }
            System.out.println(cur);
        }
    }
    
    
}