This is not homework.
I saw this article praising Linq library and how great it is for doing combinatorics stuff, and I thought to myself: Python can do it in a more readable fashion.
After half hour of dabbing with Python I failed. Please finish where I left off. Also, do it in the most Pythonic and efficient way possible please.
from itertools import permutations
from operator import mul
from functools import reduce
glob_lst = []
def divisible(n): return (sum(j*10^i for i,j in enumerate(reversed(glob_lst))) % n == 0)
oneToNine = list(range(1, 10))
twoToNine = oneToNine[1:]
for perm in permutations(oneToNine, 9):
for n in twoToNine:
开发者_如何学运维 glob_lst = perm[1:n]
#print(glob_lst)
if not divisible(n):
continue
else:
# Is invoked if the loop succeeds
# So, we found the number
print(perm)
Thanks!
Here's a short solution, using itertools.permutations:
from itertools import permutations
def is_solution(seq):
return all(int(seq[:i]) % i == 0 for i in range(2, 9))
for p in permutations('123456789'):
seq = ''.join(p)
if is_solution(seq):
print(seq)
I've deliberately omitted the divisibility checks by 1 and by 9, since they'll always be satisfied.
Here's my solution. I like all things bottom-up ;-). On my machine it runs about 580 times faster (3.1 msecs vs. 1.8 secs) than Marks:
def generate(digits, remaining=set('123456789').difference):
return (n + m
for n in generate(digits - 1)
for m in remaining(n)
if int(n + m) % digits == 0) if digits > 0 else ['']
for each in generate(9):
print(int(each))
EDIT: Also, this works, and twice as fast (1.6 msecs):
from functools import reduce
def generate():
def digits(x):
while x:
x, y = divmod(x, 10)
yield y
remaining = set(range(1, 10)).difference
def gen(numbers, decimal_place):
for n in numbers:
for m in remaining(digits(n)):
number = 10 * n + m
if number % decimal_place == 0:
yield number
return reduce(gen, range(2, 10), remaining())
for each in generate():
print(int(each))
Here's my solution (not as elegant as Mark's, but it still works):
from itertools import permutations
for perm in permutations('123456789'):
isgood = 1
for i in xrange(9):
if(int(''.join(perm[:9-i])) % (9-i)):
isgood = 0
break
if isgood:
print ''.join(perm)
this is my solution, it is very similar to Marks, but it runs about twice as fast
from itertools import permutations
def is_solution(seq):
if seq[-1]=='9':
for i in range(8,1,-1):
n = -(9-i)
if eval(seq[:n]+'%'+str(i))==0:
continue
else:return False
return True
else:return False
for p in permutations('123456789'):
seq = ''.join(p)
if is_solution(seq):
print(seq)
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