54 lines
1.3 KiB
Python
54 lines
1.3 KiB
Python
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""" day 7 part 2 """
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import fileinput
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import typing
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def has_solution(goal, operands):
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# print(f'goal={goal} operands={operands}')
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if len(operands) == 0:
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return ''
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if len(operands) == 1:
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# print(f'{goal} == {operands[0]}?')
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return goal if goal == operands[0] else ''
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# check add
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here = operands[-1]
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subgoal = operands[:-1]
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if goal > here:
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if prev := has_solution(goal - here, subgoal):
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# print(f'{goal - here} + {here}?')
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return f'{prev} + {here}'
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if here == 0 or (goal / here == goal // here):
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if prev := has_solution(goal // here, subgoal):
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# print(f'{goal / here} * {here}?')
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return f'{prev} * {here}'
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suffix = str(here)
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if str(goal).endswith(suffix) and str(goal) != suffix:
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if prev := has_solution(int(str(goal).removesuffix(suffix)), subgoal):
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return f'{prev} || {here}'
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return ''
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count = 0
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for line in fileinput.input():
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goal, _, expr = line.strip().partition(':')
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# print(f'{goal} - {expr}')
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goal = int(goal)
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operands = [int(term) for term in expr.strip().split()]
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solution = has_solution(goal, operands)
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if solution:
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print(f'{goal} = {solution}')
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count += goal
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print(count)
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