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);