将循环转换为递归[连续发现平日]

Question

我有几个嵌套for循环，试图找到连续和非连续的工作日将它们打印为字符串。这里有一个工作循环的例子：

week = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'] 
days1 = ['Mon', 'Tue', 'Wed', 'Fri', 'Sat'] 

def is_consecutive(d1, d2): 
    for i in range(0, len(week) - 1): 
     if d1 == week[i] and d2 == week[i + 1]: 
      return True 
    return False 

def get_week_string(days): 
    string = '' 
    i = 0 
    next_day = 1 
    while i < len(days): 
     if i < len(days) - 1 and is_consecutive(days[i], days[i + 1]): 
      for j in range(i, len(days) - 1): 
       if is_consecutive(days[j], days[j + 1]): 
        next_day = j + 1 
       else: 
        break 
      string = string + days[i] + " - " + days[next_day] + ", " 
      i = next_day + 1 
     else: 
      string = string + days[i] + ", " 
      i += 1 

    if string[-2:] == ', ': 
     string = string[:-2] 
    return string 

print get_week_string(days1) 
# prints Mon - Wed, Fri - Sat 

我最初试图用递归来解决这个问题，但是失败了。现在我已经有了一个可行的例子，我一直在进行更多的刺探，但是真的可以让我的头脑转向它。我使其工作的想法是这样的：

def recursive_weekdays(days, index): 
    # Base case 
    if index == len(days) - 1: 
     return days[index] 

    if is_consecutive(days[index], days[index + 1]): 
     return days[index] + " - " + recursive_weekdays(days, index + 1) 

    # ... blank here :(
    # can't figure out more :/ 

print recursive_weekdays(days, 0) 

在搞清楚了这一点，不仅使我快乐，也让我睡今晚我不能让我的脑海里过任何帮助：P

编辑：这里有一些测试用例。

days1 = ['Mon', 'Tue', 'Wed', 'Fri', 'Sat'] 
days2 = ['Mon', 'Tue', 'Wed', 'Fri', 'Sat', 'Sun'] 
days3 = ['Mon', 'Tue', 'Sun'] 
days4 = ['Wed','Thu', 'Sun'] 
days5 = ['Wed','Fri', 'Sat'] 

days1 -> Mon - Wed, Fri - Sat 
days2 -> Mon - Wed, Fri - Sun 
days3 -> Mon - Tue, Sun 
days4 -> Wed - Thu, Sun 
days5 -> Wed, Fri - Sat 

Answer 1

我想这应该对所有的情况下工作（虽然不是严格测试）

week = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'] 
days1 = ['Mon', 'Tue', 'Wed', 'Fri', 'Sat'] 
days2 = ['Mon', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'] 
days3 = ['Mon', 'Wed', 'Thu', 'Sat', 'Sun'] 

def is_consecutive(d1, d2): 
    for i in range(0, len(week) - 1): 
     if d1 == week[i] and d2 == week[i + 1]: 
      return True 
    return False 


def recursive_weekdays(days, index, in_range=False): 
    # Base case 
    if index == len(days) - 1: 
     return days[index] 

    if is_consecutive(days[index], days[index + 1]): 
     if not in_range: 
      return days[index] + " - " + recursive_weekdays(days, index + 1, True) 
     else: 
      return recursive_weekdays(days, index + 1, in_range) 

    return days[index] + ", " + recursive_weekdays(days, index + 1) 

print recursive_weekdays(days1, 0) 
print recursive_weekdays(days2, 0) 
print recursive_weekdays(days3, 0) 

输出

Mon - Wed, Fri - Sat 
Mon, Wed - Sun 
Mon, Wed - Thu, Sat - Sun 

这里的窍门是-时后只返回一个值你不再处于连续的日子里。

编辑
以下是输出值从测试情况：

Mon - Wed, Fri - Sat 
Mon - Wed, Fri - Sun 
Mon - Tue, Sun 
Wed - Thu, Sun 
Wed, Fri - Sat