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);
         }
     }

 }