编程之美——买书问题

来源：互联网发布：angularjs源码解析编辑：程序博客网时间：2024/05/20 12:24

题目：

java实现：

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

public class BuyBook {
   private final float price = 8f;
   private float minTotalPrice;//最少付出的总钱数
   private Integer[] arrNum;//５本书，各买多少本
   private List<Integer> steps;//最小分配方案
   private List<Integer> tempSteps;//中间临时最小分配方案

   private enum PERCENT{//折扣
       ONE(1.0f), TWO(0.95f), THREE(0.9f), FOUR(0.8f), FIVE(0.75f);

       private float value = 0f;
       private PERCENT(float value){
           this.value = value;
       }

       public float value(){
           return this.value;
       }

       public static PERCENT valueOf(int value){
           switch (value) {
           case 1:
               return ONE;
           case 2:
               return TWO;
           case 3:
               return THREE;
           case 4:
               return FOUR;
           case 5:
               return FIVE;
           default:
               return null;
           }
       }

   }

   public BuyBook(Integer[] arrNum) {
       if(arrNum.length != 5)
           return;
       this.arrNum = descSort(arrNum);
       minTotalPrice = 0f;
       for (int i = 0; i < arrNum.length; i++){
           this.minTotalPrice += arrNum[i] * price;
       }
       steps = new ArrayList<Integer>();
       tempSteps = new ArrayList<Integer>();

       findMinPrice(arrNum, 0f);
   }

   private void findMinPrice(Integer[] arrNum, float total){
       if(arrNum.length != 5)
           return ;

       if(arrNum[0] == 0){//结束条件
           if(total < minTotalPrice){
               this.minTotalPrice = total;
               steps.clear();
               steps.addAll(tempSteps);
           }
           tempSteps.clear();
       }

       Integer[] temparrNum = arrNum.clone();
       float temp = 0f;

       for(int i = 5; i >= 1; i--){
           temp = 0f;
           if(arrNum[i-1] >= 1){
               tempSteps.add(i);
               temp = i * price * PERCENT.valueOf(i).value;
               for(int k = 0; k < 5; k++){
                   temparrNum[k] = arrNum[k];
                   if(k < i)
                       temparrNum[k] = arrNum[k] - 1;
               }
               temparrNum = descSort(temparrNum);
               findMinPrice(temparrNum, total + temp);
           }
       }
   }

   /**
   * 将arrNum2中元素逆序排序
   * @param arrNum2
   * @return
   */
   private Integer[] descSort(Integer[] arrNum2) {

       Arrays.sort(arrNum2, new Comparator<Integer>() {

           @Override
           public int compare(Integer o1, Integer o2) {
               // TODO Auto-generated method stub
               return o1 > o2? -1 : 1;
           }
       });
       return arrNum2;
   }

   public static void main(String[] args) {
       Integer[] Y = new Integer[]{2,2,2,1,1};
       BuyBook books = new BuyBook(Y);

       System.out.println(books.minTotalPrice);
       for(int i = 0; i < books.steps.size(); i++){
           System.out.println(books.steps.get(i));
       }
   }

}

输出：

51.2
4
4

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