題目連接：http://www.checkio.org/mission/friends/
題目：
For the mission "How to find friends" , it’s nice to have access to a specially made data structure. In this mission we will realize a data structure which we will use to store and work with a friend network.
The class "Friends" should contains names and the connections between them. Names are represented as strings and are case sensitive. Connections are undirected, so if "sophia" is connected with "nikola", then it's also correct in reverse.
class Friends(connections)
Returns a new Friends instance. "connections" is an iterable of sets with two elements in each. Each connection contains two names as strings. Connections can be repeated in the initial data, but inside it's stored once. Each connection has only two states - existing or not.
>>> Friends(({"a", "b"}, {"b", "c"}, {"c", "a"}, {"a", "c"}))
>>> Friends([{"1", "2"}, {"3", "1"}])
add(connection)
Add a connection in the instance. "connection" is a set of two names (strings). Returns True if this connection is new. Returns False if this connection exists already.
>>> f = Friends([{"1", "2"}, {"3", "1"}])
>>> f.add({"1", "3"})
False
>>> f.add({"4", "5"})
True
remove(connection)
Remove a connection from the instance. "connection" is a set of two names (strings). Returns True if this connection exists. Returns False if this connection is not in the instance.
>>> f = Friends([{"1", "2"}, {"3", "1"}])
>>> f.remove({"1", "3"})
True
>>> f.remove({"4", "5"})
False
names()
Returns a set of names. The set contains only names which are connected with somebody.
>>> f = Friends(({"a", "b"}, {"b", "c"}, {"c", "d"}))
>>> f.names()
{"a", "b", "c", "d"}
>>> f.remove({"d", "c"})
True
>>> f.names()
{"a", "b", "c"}
connected(name)
Returns a set of names which is connected with the given "name". If "name" does not exist in the instance, then return an empty set.
>>> f = Friends(({"a", "b"}, {"b", "c"}, {"c", "a"}))
>>> f.connected("a")
{"b", "c"}
>>> f.connected("d")
set()
>>> f.remove({"c", "a"})
True
>>> f.connected("c")
{"b"}
>>> f.remove({"c", "b"})
True
>>> f.connected("c")
set()
In this mission all data will be correct and you don't need to implement value checking.
Input: Statements and expression with the Friends class.
Output: The behaviour as described.
How it is used: Here you will implement a class with mutable states. This is not a simple structure with a couple of functions, but object representation with more complex structure.
Precondition: All data is correct.
代碼：
class Friends:
def __init__(self, connections):
self.connections = connections
self.li = list(connections)
#只有列表能操作，元組不能操作
def add(self, connection):
#self.connection = connection
if connection in self.li:
return False
else:
self.li.append(connection)
return True
def remove(self, connection):
#self.connection = connection
if connection in self.li:
self.li.remove(connection)
return True
else:
return False
def names(self):
name =[]
for i,j in self.li: #因爲迭代對象有（a,b）的形式，這樣子能表示這個兩個子元素
if i not in name:
name.append(i)
if j not in name:
name.append(j)
return set(name)
def connected(self, name):
l = []
for x,y in self.li:
if name == x:
l.append(y)
elif name == y:
l.append(x)
return set(l)
if __name__ == '__main__':
#These "asserts" using only for self-checking and not necessary for auto-testing
letter_friends = Friends(({"a", "b"}, {"b", "c"}, {"c", "a"}, {"a", "c"}))
digit_friends = Friends([{"1", "2"}, {"3", "1"}])
assert letter_friends.add({"c", "d"}) is True, "Add"
assert letter_friends.add({"c", "d"}) is False, "Add again"
assert letter_friends.remove({"c", "d"}) is True, "Remove"
assert digit_friends.remove({"c", "d"}) is False, "Remove non exists"
assert letter_friends.names() == {"a", "b", "c"}, "Names"
assert letter_friends.connected("d") == set(), "Non connected name"
assert letter_friends.connected("a") == {"b", "c"}, "Connected name"
class Friends(set):
def __init__(self, pairs=set()):
super().__init__(map(frozenset, pairs))
def add(self, pair):
if pair in self: return False
super().add(frozenset(pair))
return True
def remove(self, pair):
if pair not in self: return False
super().remove(pair)
return True
def names(self):
return set().union(*self)
def connected(self, name):
return Friends(filter({name}.issubset, self)).names() - {name}
class Friends():
def __init__(self, connections):
self.all_connection = list(connections)
def add(self, connection):
if connection in self.all_connection:
return False
else:
self.all_connection.append(connection)
return True
def remove(self, connection):
if connection in self.all_connection:
self.all_connection.remove(connection)
return True
else:
return False
def names(self):
return reduce(lambda a,b: a.union(b), self.all_connection)
def connected(self, name):
related = [pair for pair in self.all_connection if name in pair]
if related:
related = reduce(lambda a,b: a.union(b), related)
related.remove(name)
return related
else:
return set([])