plus minus

This commit is contained in:
Ivan Malison 2015-11-17 06:03:44 -08:00
parent 8fc2cd4141
commit efa0de090f

View File

@ -0,0 +1,63 @@
def groupings(numbers):
if len(numbers) == 0:
raise StopIteration()
if len(numbers) == 1:
yield ((numbers[0],),)
raise StopIteration()
this_number = numbers[0]
this_tuple = (this_number,)
next_groupings = groupings(numbers[1:])
for grouping in next_groupings:
yield (this_tuple,) + grouping
yield (this_tuple + grouping[0],) + grouping[1:]
def plus_minus_n(numbers, n):
for grouping in groupings(numbers):
numbers = map(group_to_int, grouping)
pms = plus_minuses(len(numbers) - 1)
for pm in pms:
result = compute(numbers, pm)
string = generate_string(numbers, pm)
if result == n:
yield string
def generate_string(numbers, pms):
string = ''
for number in numbers:
string += '{0}'.format(number)
if pms:
string += '+' if pms[0] is PLUS else '-'
pms = pms[1:]
return string
def compute(numbers, plus_minus):
sum = numbers[0]
remaining = numbers[1:]
while remaining:
if plus_minus[0] == PLUS:
sum += remaining[0]
else:
sum -= remaining[0]
remaining = remaining[1:]
plus_minus = plus_minus[1:]
return sum
def group_to_int(group):
return int(''.join(map(str, group)))
PLUS = object()
MINUS = object()
def plus_minuses(n):
if n == 0:
yield ()
raise StopIteration()
for pm in plus_minuses(n-1):
yield (PLUS,) + pm
yield (MINUS,) + pm