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

  1 class Strategy:
  2     def __init__(self, items):
  3         self.items = items;
  4         self.rate = self.get_discount_rate();
  5    
  6     def get_discount_rate(self):
  7         if len(self.items) == 5:
  8             return 0.75;
  9         if len(self.items) == 4:
 10             return 0.8;
 11         if len(self.items) == 3:
 12             return 0.9;
 13         if len(self.items) == 2:
 14             return 0.95;
 15         return 1.0;
 16 
 17     def get_price(self):
 18         return self.total_price() * self.rate;
 19 
 20     def total_price(self):
 21         price = 0.0;
 22         for item in self.items:
 23             price += item.book.price;
 24         return price;
 25 
 26     def count(self):
 27         return len(self.items);
 28     
 29 
 30 class StrategyOptimizer:
 31     def optimize(self, strategies):
 32         found = False;
 33         while True:
 34             found = self.replace_53_with_44(strategies);
 35             if not found:
 36                 break;
 37         return strategies;
 38 
 39     def replace_53_with_44(self, strategies):
 40         strategyMap = {};
 41         strategyMap.clear();
 42         for i in range(0, len(strategies)):
 43             strategy = strategies[i];
 44             strategyMap[strategy.count()] = i;
 45 
 46         if (strategyMap != None and len(strategyMap) != 0):
 47             if (strategyMap.get(5, None) != None and strategyMap.get(3, None) != None):
 48                 self.move_book(strategies[strategyMap[5]], strategies[strategyMap[3]]);
 49                 return True;
 50         return False;
 51 
 52     def move_book(self, source, dest):
 53         item = self.findAnyDiff(source, dest);
 54         if item == None:
 55             return;
 56         source.items.remove(item);
 57         source.rate = source.get_discount_rate();
 58         dest.items.extend([item]);
 59         dest.rate = source.get_discount_rate();
 60         return;
 61     
 62     def findAnyDiff(self, source, dest):
 63         for item in source.items:
 64             if item not in dest.items:
 65                 return item;
 66         return None;
 67 
 68 class Book:
 69     def __init__(self, index, name, price):
 70         self.index = index;
 71         self.name = name
 72         self.price = price
 73 
 74 class Item:
 75     def __init__(self, book, count):
 76         self.book = book
 77         self.count = count
 78 
 79 class Cart:
 80     items = [];
 81     def add_item(self, item):
 82         self.items.append(item);
 83 
 84 def pick_most_books(cart):
 85     items = [];
 86     for i in range(0, len(cart.items)):
 87         item = cart.items[i];
 88         if item.count == 0:
 89             continue;
 90         items.append(Item(item.book, 1));
 91         cart.items[i].count -= 1;
 92     return items;
 93 
 94 def is_empty(cart):
 95     for item in cart.items:
 96         if item.count > 0:
 97             return False;
 98     return True;
 99 
100 def count_price(strategies):
101     price = 0;
102     for s in strategies:
103         price += s.get_price();
104     return price;
105 
106 def find_best_solution(cart):
107     strategies = [];
108     price = 0.0;
109     while not is_empty(cart):
110         items = pick_most_books(cart);
111         strategy = Strategy(items);
112         strategies.append(strategy);
113     return strategies;
114 
115 def count_best_price(cart):
116     strategies = find_best_solution(cart);
117     so = StrategyOptimizer();
118     strategies = so.optimize(strategies)
119     price = count_price(strategies);
120     print(price);
121 
122 if __name__ == '__main__':
123     item_1 = Item(Book("#1.", "Philosophy Stone", 8), 2);
124     item_2 = Item(Book("#2.", "Secret Chamber", 8), 2);
125     item_3 = Item(Book("#3.", "Prisoner of Azkaban", 8), 2);
126     item_4 = Item(Book("#4.", "Goblet of Fire", 8), 1);
127     item_5 = Item(Book("#5.", "The Order of Phoenix", 8), 1);
128     
129     cart = Cart();
130     cart.add_item(item_1);
131     cart.add_item(item_2);
132     cart.add_item(item_3);
133     cart.add_item(item_4);
134     cart.add_item(item_5);
135 
136     count_best_price(cart);