第一次写python

这是一个在BJDP上学习Coding Kata的时候用到的一个练习，原来打算用Java写的，但是一想正好是学习的好机会。

就用Python了。第一次，写的有些复杂。

这个题目是关于购买图书的打折信息的。

题目来源：

http://codingdojo.org/cgi-bin/wiki.pl?KataPotter

 class Strategy:
     def __init__(self, items):
         self.items = items;
         self.rate = self.get_discount_rate();

     def get_discount_rate(self):
         if len(self.items) == 5:
             return 0.75;
         if len(self.items) == 4:
             return 0.8;
         if len(self.items) == 3:
             return 0.9;
         if len(self.items) == 2:
             return 0.95;
         return 1.0;

     def get_price(self):
         return self.total_price() * self.rate;

     def total_price(self):
         price = 0.0;
         for item in self.items:
             price += item.book.price;
         return price;

     def count(self):
         return len(self.items);

 class StrategyOptimizer:
     def optimize(self, strategies):
         found = False;
         while True:
             found = self.replace_53_with_44(strategies);
             if not found:
                 break;
         return strategies;

     def replace_53_with_44(self, strategies):
         strategyMap = {};
         strategyMap.clear();
         for i in range(0, len(strategies)):
             strategy = strategies[i];
             strategyMap[strategy.count()] = i;

         if (strategyMap != None and len(strategyMap) != 0):
             if (strategyMap.get(5, None) != None and strategyMap.get(3, None) != None):
                 self.move_book(strategies[strategyMap[5]], strategies[strategyMap[3]]);
                 return True;
         return False;

     def move_book(self, source, dest):
         item = self.findAnyDiff(source, dest);
         if item == None:
             return;
         source.items.remove(item);
         source.rate = source.get_discount_rate();
         dest.items.extend([item]);
         dest.rate = source.get_discount_rate();
         return;

     def findAnyDiff(self, source, dest):
         for item in source.items:
             if item not in dest.items:
                 return item;
         return None;

 class Book:
     def __init__(self, index, name, price):
         self.index = index;
         self.name = name
         self.price = price

 class Item:
     def __init__(self, book, count):
         self.book = book
         self.count = count

 class Cart:
     items = [];
     def add_item(self, item):
         self.items.append(item);

 def pick_most_books(cart):
     items = [];
     for i in range(0, len(cart.items)):
         item = cart.items[i];
         if item.count == 0:
             continue;
         items.append(Item(item.book, 1));
         cart.items[i].count -= 1;
     return items;

 def is_empty(cart):
     for item in cart.items:
         if item.count > 0:
             return False;
     return True;

 def count_price(strategies):
     price = 0;
     for s in strategies:
         price += s.get_price();
     return price;

 def find_best_solution(cart):
     strategies = [];
     price = 0.0;
     while not is_empty(cart):
         items = pick_most_books(cart);
         strategy = Strategy(items);
         strategies.append(strategy);
     return strategies;

 def count_best_price(cart):
     strategies = find_best_solution(cart);
     so = StrategyOptimizer();
     strategies = so.optimize(strategies)
     price = count_price(strategies);
     print(price);

 if __name__ == '__main__':
     item_1 = Item(Book("#1.", "Philosophy Stone", 8), 2);
     item_2 = Item(Book("#2.", "Secret Chamber", 8), 2);
     item_3 = Item(Book("#3.", "Prisoner of Azkaban", 8), 2);
     item_4 = Item(Book("#4.", "Goblet of Fire", 8), 1);
     item_5 = Item(Book("#5.", "The Order of Phoenix", 8), 1);

     cart = Cart();
     cart.add_item(item_1);
     cart.add_item(item_2);
     cart.add_item(item_3);
     cart.add_item(item_4);
     cart.add_item(item_5);

     count_best_price(cart);