在电商平台通常会有一些优惠措施,比如以优惠券、定金或者代币之类的形式在下单时给予用户直观的减免金额.一般用户领取店铺优惠券,优惠券有不同的使用条件,满足条件时方可使用.定金为用户自己向店铺购买的形式,定金在特定的时间或者针对某个商品可以膨胀使用,膨胀出多余的部分相当商家让利,可以优惠购买.代币为商家以不同面值发放给用户,以抵扣下单金额.
问题描述
假设某个店铺有好多不同使用条件的优惠券比如满20减去5,满20减10,每满20减5,每满20减21(其实我也不知道这个的意义什么,但是产品说就要发这样的券),然后用户还分别购买了20,30,60的定金,当用户下单金额为200元时,用户自己就难以选择,无法立即计算出支付最少的钱购买此单商品,所以需要我们计算匹配出一个最划算的组合给用户.当然优惠券和定金只能各选一个.
解决思路
作为用户来讲,当然优先使用优惠券,因为优惠券为商家赠与而定金时自己购买,故支付金额=订单金额-优惠券的优惠金额(因为包含每满类型,所以不一是优惠券面值)-定金.那么大概思路就是定金和优惠券的组合,相当于两层for循环,然后按照这个公式算出支付金额大于等于零的那个值就可以了.思路时挺简单,但是优惠券的逻辑就有点复杂,以为优惠券自身就有好多种组合,例如满10减5,满10减8,每满10减8,满5减8,每满5减8,所以优惠券的顺序应该根据是否每满、优惠满足金额、优惠金额排序.
具体方案
先定义好优惠券、定金和最优组合的模型
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| public class Coupon {
public String id;
public double spending;
public int every;
public double discount;
}
public class Booking {
public String id;
public double amount;
}
public class BestCombination {
public double bookingAmount;
public double couponAmount;
public Booking booking;
public Coupon coupon;
public BestCombination(Booking booking, Coupon coupon, double bookingAmount, double couponAmount) {
this.booking = booking;
this.coupon = coupon;
this.bookingAmount = bookingAmount;
this.couponAmount = couponAmount;
}
}
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然后先对优惠券和定金列表排序
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| private List<Coupon> initCoupon(double totalPrice, List<Coupon> coupons) {
List<Coupon> result = new ArrayList<>();
if (coupons.size() > 0) {
for (Coupon b : coupons) {
if (b.spending <= totalPrice) {
result.add(b);
}
}
}
Collections.sort(result, new Comparator<Coupon>() {
@Override
public int compare(Coupon o1, Coupon o2) {
int compareEvery = Integer.compare(o2.every, o1.every);
if (compareEvery == 0) {
int compareSpending = Double.compare(o1.spending, o2.spending);
if (compareSpending == 0) {
return Double.compare(o1.discount, o2.discount);
} else {
return compareSpending;
}
} else {
return compareEvery;
}
}
});
Coupon emptyCoupon = new Coupon();
emptyCoupon.discount = 0;
emptyCoupon.spending = 0;
emptyCoupon.id = "-1";
emptyCoupon.every = 0;
result.add(emptyCoupon);
return result;
}
private List<Booking> initBooking(List<Booking> bookings) {
List<Booking> result = new ArrayList<>();
if (bookings.size() > 0) {
result.addAll(bookings);
}
Booking emptyBooking = new Booking();
emptyBooking.amount = 0;
emptyBooking.id = "-1";
result.add(emptyBooking);
return result;
}
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最后就可以根据订单金额、优惠券和定金计算出最优的组合
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|
public static BestCombination calculatorBestCombination(double totalPrice, List<Coupon> coupons, List<Booking> bookings) {
SortedMap<Double, BestCombination> map = new TreeMap<>();
double couponPrice;
for (Coupon c : coupons) {
for (Booking b : bookings) {
double tempPrice = totalPrice;
if (c.every == 1) {
couponPrice = Math.floor(tempPrice / c.spending) * c.discount;
} else {
couponPrice = c.discount;
}
tempPrice = tempPrice - couponPrice;
tempPrice = tempPrice - b.amount;
if (!(tempPrice < 0 && b.amount > 0)) {
if (map.containsKey(tempPrice)) {
BestCombination best = map.get(tempPrice);
if (best.bookingAmount >= b.amount) {
map.put(tempPrice, new BestCombination(b, c, b.amount, couponPrice));
}
} else {
map.put(tempPrice, new BestCombination(b, c, b.amount, couponPrice));
}
}
}
}
BestCombination bestCombination;
if (map.size() <= 0) {
bestCombination = null;
} else {
if (map.firstKey() >= 0) {
bestCombination = map.get(map.firstKey());
} else {
double key = 0;
for (Map.Entry<Double, BestCombination> e : map.entrySet()) {
System.out.println(e.getKey() + " " + e.getValue().toString());
if (e.getValue().booking.amount > 0) {
if (e.getKey() >= 0) {
break;
} else {
key = e.getKey();
}
} else {
if (e.getKey() > 0) {
break;
} else {
key = e.getKey();
}
}
}
bestCombination = map.get(key);
}
}
return bestCombination;
}
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计算最划算的组合,重点在于计算前的数据排序、计算时替换相同支付金的组合和计算后最优组合的选择.***项目地址***可以运行测试用例.