给你一部分钱和一些不同价钱的商品，如何在最多买K件商品的情况下尽可能多的花掉手里的钱。

举例：口袋里的钱数： 10;   K=2     产品价格: [3, 6, 8, 7, 9]   输出 3, 7

 package BuyGoods;

 import java.util.*;

 public class Solution {

     static int minRemain = 0;

     public ArrayList<Integer> optimize(int money, int[] prices, int k) {

         ArrayList<Integer> result = new ArrayList<Integer>();

         ArrayList<Integer> path = new ArrayList<Integer>();

         minRemain = money;

         helper(result, path, money, prices, 0, k);

         return result;

     }

     public void helper(ArrayList<Integer> result, ArrayList<Integer> path, int remain, int[] prices, int pos, int times) {

         if (remain < 0 || times<0) return;

         if (remain < minRemain) {

             minRemain = remain;

             result.clear();

             result.addAll(path);

         }

         for (int i=pos; i<prices.length; i++) {

             path.add(prices[i]);

             helper(result, path, remain-prices[i], prices, i+1, times-1);

             path.remove(path.size()-1);

         }

     }

     /**

      * @param args

      */

     public static void main(String[] args) {

         // TODO Auto-generated method stub

         Solution sol = new Solution();

         ArrayList<Integer> result = sol.optimize(10, new int[]{7,8,1,6,9}, 3);

         System.out.println(result);

     }

 }