Python：每日一题 195,Python交流,技术交流,鱼C论坛

可乐必须加冰 发表于 2018-8-7 20:14:32

def fun(dict, key):
list1 = []
key1 = key
for i in dict:
   list1.append(i)
if key not in list1:
   return "输入错误，没有该key值"
else:
   while True:
         if key not in list1:
            return key
         elif dict == key1:
            return None
         else:
            key = dict

spacecowboy 发表于 2018-8-7 21:43:04

dict1 = {'A':'B','B':'C','C':'D','D':'A'}
def fun(dict,key):
abkey = key
while dict1 in dict1:
   key = dict1
   if key == abkey:
         dict = None
         break
return dict1

ErTian 发表于 2018-8-8 00:24:11

def test195(dic,key):
temp = []
temp.append(key)
for i in range(len(dic)):
   if dic in temp:
         return None
   else:
         key = dic
         temp.append(key)
else:
   return key

dict1 = {"A": "B", "B": "C", "C": "D", "D": "A", "E": "F"}
dict2 = {"A": "B", "B": "C", "C": "D"}
print(test195(dict1,'A'))
print(test195(dict2,'A'))

claws0n 发表于 2018-8-8 21:19:34

def find_key(input_dict, x):
return find_key(input_dict, input_dict)

def fun195(input_dict, x):
   try:
         y = find_key(input_dict, x)
   except KeyError as e:
         print(e)
   except RecursionError:
         print(None)

dict1 = {"A": "B", "B": "C", "C": "D"}
##dict1 = {"A": "B", "B": "C", "C": "D", "D": "A", "E": "F"}

print('-----try A')
fun195(dict1,'A')

print('-----try D')
fun195(dict1,'D')

print('-----try E')
fun195(dict1,'E')

print('-----try F')
fun195(dict1,'F')

学学看看 发表于 2018-8-9 14:31:42

yjsx86 发表于 2018-8-9 15:33:26

dict1 = {"A": "B", "B": "C", "C": "D", "D": "A", "E": "F"}
def func(Dict, Item):
start = Item
times = 0
while True:
   if times > len(Dict):
         return None
   next = Dict
   if next in Dict.keys():
         Item = next
         times += 1
   else:
         return next

if __name__ == '__main__':
print(func(dict1,'A'))

archlzy 发表于 2018-8-9 16:23:47

def fun195(dict1, key):
i = 0
while dict1 in list(dict1.keys()):
   i += 1
   key = dict1
   if i >= len(list(dict1.keys())):
         return None
return dict1

dict1 = {"A": "B", "B": "C", "C": "D", "D": "A", "E": "F"}
key = "A"

fun195(dict1, key)

wwq天天 发表于 2018-8-9 17:16:54

def fun(dict1,a):
i=1
c=a
try:
   while i>0:
         b=dict1
         if (len(b)>0):
            i=1
            a=b
            if (str(a)==c):
               a=None
               break
         else:
            i=0
            break
except:
   pass

return a

if __name__=='__main__':

dict1 = {"A": "B", "B": "C", "C": "D", "D": "H", "E": "F"}
y = fun(dict1,"A")
print (y)

凌九霄 发表于 2018-8-9 21:03:23

dict1 = {"A": "B", "B": "C", "C": "D", "D": "Q", "E": "F"}

这条貌似很多也过不了啊，输入key='F' ,正确应该返回None，很多返回F

冬雪雪冬 发表于 2018-8-9 21:05:12

凌九霄发表于 2018-8-9 21:03
dict1 = {"A": "B", "B": "C", "C": "D", "D": "Q", "E": "F"}

这条貌似很多也过不了啊，输入key='F' , ...

主要是题目中没有要求检测不存在的key，所以就不强求大家了

claws0n 发表于 2018-8-9 23:55:19

冬雪雪冬发表于 2018-8-9 21:05
主要是题目中没有要求检测不存在的key，所以就不强求大家了

当时候有点迟疑，但觉得竟然题目没有特别要求，才用抛出异常的手法{:5_96:}

冬雪雪冬 发表于 2018-8-10 08:12:16

claws0n 发表于 2018-8-9 23:55
当时候有点迟疑，但觉得竟然题目没有特别要求，才用抛出异常的手法

你考虑的周全

Henriz 发表于 2018-8-10 08:17:27

感谢版主仔细评分，没有用到递归算法，还是要多学习

a641743376 发表于 2018-8-10 16:49:07

d1 = {"A": "B", "B": "C", "C": "D", "E": "F"}
d2 = {"A":"B", "B":"C","C":"D","D":"B"}
def f(d,s):
tmp1 = d
tmp2 = None
if tmp1 not in d.keys():
   tmp2 = tmp1
else:
   for k, v in d.items():
         if k != s and v not in d.keys():
            tmp2 = v
            break
return tmp2

print(f(d1, "A")) #链状
print(f(d1, "E")) #单独
print(f(d2, "A")) #循环

graceasyi 发表于 2018-8-14 10:33:54

本帖最后由 graceasyi 于 2018-8-14 10:35 编辑

第一种方法只能处理顺序的情况，就是题目中的dict。第二种方法可处理非顺序情况。

def fun195_1(dict1, key):
tmp = []
for k, v in dict1.items():
   tmp.append(k)
   if key == k:
         key = v
return None if key in tmp else key

def fun195_2(dict1, key):
v = dict1
tmp = []
while True:
   tmp.append(v)
   try:
         v = dict1
         if v in tmp:
            return None
   except KeyError:
         break
return v

d1 = {"A": "B", "B": "C", "C": "D", "E": "F"}
d2 = {"A": "B", "B": "C", "C": "D", "D": "B"}
d3 = {"A": "B", "C": "D", "B": "C", "D": "F", "F": "E", "E": "G"}
d4 = {"A": "B", "C": "D", "B": "C", "D": "F", "F": "E", "E": "D"}
print(fun195_2(d1, 'A'))
print(fun195_2(d1, 'E'))
print(fun195_2(d2, 'A'))
print(fun195_2(d3, 'B'))
print(fun195_2(d4, 'A'))

结果：
D
F
None
G
None

子沙发表于 2018-9-24 19:01:26

def fun_195(dict1,key1,temp=[]):
while True:
   if key1 in dict1.keys():
         temp.append(key1)
         key1=dict1
   else:
         break
   if key1 in temp:
         key1=None
         break
print(key1)

d1 = {"A": "B", "B": "C", "C": "D", "E": "F"}
d2 = {"A":"B", "B":"C","C":"D","D":"B"}
fun_195(d1,"E")
fun_195(d1,"A")
fun_195(d2,"A")

xy123151 发表于 2018-11-26 16:30:50

def f(dic1,a):
dic = dic1.copy()
while True:
   b = dic.get(a)
   dic.pop(a,None)
   if dic.get(b,None):pass
   else:
         if dic1.get(b,None):return None
         return b
   a = b

d1 = {"A": "B", "B": "C", "C": "D", "E": "F"}
d2 = {"A":"B", "B":"C","C":"D","D":"B"}
print(f(d1,'A'))
print(f(d1,'E'))
print(f(d2,'A'))

776667 发表于 2019-2-28 16:04:07

def fun195(dict_x,key):
repeat_key = []
while True:
   if key in repeat_key:
         return None
   try:
         dict_x]
   except KeyError:
         return dict_x
   repeat_key.append(key)
   key = dict_x

if __name__ == '__main__':
d1 = {'A': 'B', 'B': 'C', 'C': 'D', 'E': 'F'}
d2 = {'A':'B', 'B':'C','C':'D','D':'B'}
print(fun195(d1,'A'))
print(fun195(d1,'E'))
print(fun195(d2,'A'))

永恒的蓝色梦想 发表于 2019-7-27 21:30:20

def func(dic,key):
originalkey=key
while 1:
try:key=dic
except:return key
if key==originalkey:return

小陨aoq 发表于 2020-8-14 20:56:38

def fun(dic, val):
found = []

while dic.get(val):
   found.append(val)
   val = dic.pop(val)
   if val in found:
         return None
else:
   return val

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