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