pack.py

# -*- coding: utf-8 -*-

MAX_TAX = 500
MAX_PRICE = 1000

class Item(object):

    """商品类"""

    def __init__(self, price, tax_rate, category):
        """
        :price: 商品单价
        :tax_rate: 商品税率
        :category: 商品类别
        """
        self.price = price
        self.tax_rate = tax_rate
        self.category = category
            
    @property
    def tax(self):
        """
        :returns: 单件商品的关税
        """
        return self.price * self.tax_rate
    
    def __repr__(self):
        return 'price: %s tax: %s category: %s' % (self.price, self.tax, self.category)

def tax_sum(items):
    return sum([item.tax for item in items])

def amount_sum(items):
    return sum([item.price for item in items])

def pack_sorted_items(items, packages):
    """
    打包商品
    """
    count = len(items)
    if count == 0:
        return 
    elif count == 1:
        packages.append(items)
        return

    remain_items, suitable_items = get_suitable_items(items[-1], items[:-1])
    packages.append(suitable_items)
    return pack_sorted_items(remain_items, packages)

def get_suitable_items(item, items):
    """
    从商品库items里面选取符合条件且不多于2个的商品
    返回剩下的商品库和打包的商品
    """
    suitable_items = [item]
    if item.category == 'SHOES':
        items, suitable_items = pick_item(items, suitable_items, 'HANDBAG')
        items, suitable_items = pick_item(items, suitable_items, 'HANDBAG')
        return items, suitable_items
    elif item.category == 'HANDBAG':
        items, suitable_items = pick_item(items, suitable_items, 'SHOES')
        items, suitable_items = pick_item(items, suitable_items, 'SHOES')
        return items, suitable_items

    suitable_items.append(items[0])
    first_picked_item = items[0]
    items.remove(items[0])
    # 通过第一个物品的类别选取第二个物品
    if first_picked_item.category == 'SHOES':
        items, suitable_items = pick_item(items, suitable_items, 'HANDBAG')
    elif first_picked_item.category == 'HANDBAG':
        items, suitable_items = pick_item(items, suitable_items, 'SHOES')
    else:
        items, suitable_items = pick_item(items, suitable_items)
    return items, suitable_items

def pick_item(items, suitable_items, category=None):
    """
    选取第一个符合条件的商品
    """
    first_picked_item = items[0] if items and not category else None
    if category:
        for item in items:
            if item.category != category:
                first_picked_item = item
                break
    # 判断是否满足条件条件
    if not first_picked_item \
            or amount_sum(suitable_items) + first_picked_item.price >= MAX_PRICE \
            or tax_sum(suitable_items) + first_picked_item.tax >= MAX_TAX:
        return items, suitable_items
    # 把符合条件的商品放进包裹里面
    suitable_items.append(first_picked_item)
    items.remove(first_picked_item)
    return items, suitable_items


def pack(items):
    packages = []
    sorted_items = sorted(items, key=lambda x: x.price)
    for item in sorted_items:
        # 单价或者关税大于指定金额的商品单独打包
        if item.price >= MAX_PRICE or item.tax >= MAX_TAX:
            packages.append([item])
            sorted_items.remove(item)
    # 对剩下的商品进行打包
    pack_sorted_items(sorted_items, packages)
    return packages