趣味算法之怎样订饭最省钱

近来很多同事都在网上订餐，网上订餐基本都会有优惠，不同家的优惠策略不同，但大体上都是三种策略，比如有几家是满15减6，满30减15，满50减20。

然后我突发奇想，何不写个程序，来根据餐厅的优惠政策计算下怎样拼饭最省钱呢？于是有了下面代码：

import java.util.ArrayList;
import java.util.Scanner;

public class Lunch {

public static double[] Fee = {15, 30, 50};//满多少钱可优惠
public static double[] Dis = {6, 15, 20};//对应的优惠价格

public static double[] disCount;//折扣
public static int[] strategy;//策略
public static int[] price;//每份饭的单价
public static int[] priceCopy;//同样是每份饭的单价
public static double sumPrice = 0.0;//优惠前的总价
public static int person = 0;//共几人订餐

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
person = sc.nextInt();
price = new int[person];
priceCopy = new int[person];
for(int i=0; i<person; i++){
price[i] = sc.nextInt();
priceCopy[i] = price[i];
sumPrice += price[i];
}
disCount = new double[3];
strategy = new int[3];
for(int i=0; i<3; i++){
disCount[i] = Dis[i]/Fee[i];
}
double max = 0.0;
int maxIndex = 0;

for(int i=0; i<3; i++){
max = disCount[i];
maxIndex = i;
for(int j=0; j<3; j++){
if(disCount[j] > max){
max = disCount[j];
maxIndex = j;
}
}
strategy[i] = maxIndex;
disCount[maxIndex] = 0;
}
double save = cal();
System.out.println("总共省钱"+save+"元");
sc.close();
}
/**
* 返回节约的饭钱
* straNum 是指当前使用的打折策略的编号
* save 是指已经节省的钱
* */
private static double cal() {
double save = 0.0;
int straNum = 0;
ArrayList<Integer> choosed = new ArrayList<Integer>();

while(straNum < 3){
int index = strategy[straNum];
double pinPrice = Fee[index];
if(sumPrice < pinPrice){
straNum++;
continue;
}
choosed = new ArrayList<Integer>();
for(int add=0; true; add++){
if(sumPrice < pinPrice + add){
straNum++;
break;
}

if(choose(pinPrice+add, 0, choosed)){
sumPrice -= (pinPrice+add);
save += Dis[index];
System.out.println("此单凑出的钱数为："+(pinPrice+add));
System.out.print("由以下价格凑出：");
for(int c:choosed){
System.out.print(priceCopy[c]+" ");
}
System.out.println();
break;
}else{
int nextIndex = strategy[straNum+1];
double nextFee = Fee[nextIndex];
double nextDis = Dis[nextIndex];
int counts = (int) (((pinPrice+add)/nextFee)%1);
double nextSave = nextDis * counts;
if(nextSave > Dis[index]){
straNum++;
break;
}
}
}
}
return save;
}
/**
* 返回是否能拼出饭钱pinPrice
* @param pinPrice 要拼的饭钱
* cur 当前要处理的餐费
* choosed 存放被选择的餐费的下标
* */
private static boolean choose(double pinPrice, int cur, ArrayList<Integer> choosed){

if(pinPrice < 0)
return false;
while(cur<person && price[cur]==0){
cur++;
}
if(cur == person && pinPrice!=0)
return false;
if(pinPrice ==0 ){
return true;
}
if(choose(pinPrice - price[cur], cur+1, choosed)){
choosed.add(cur);
price[cur] = 0;
return true;
}else if(choose(pinPrice, cur+1, choosed)){
return true;
}else{
return false;
}

}

}