52 lines
1.1 KiB
Python
52 lines
1.1 KiB
Python
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operators = {
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'*': 1,
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'+': 0,
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}
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def tokenize(xs):
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result = []
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i = 0
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while i < len(xs):
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current = xs[i]
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if current in operators.keys():
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result.append(current)
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i += 1
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continue
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else:
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i += 1
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while i < len(xs) and xs[i] in {str(n) for n in range(10)}:
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current += xs[i]
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i += 1
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result.append(int(current))
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return result
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def postfix(xs):
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result = []
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s = []
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for x in xs:
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if x in operators.keys():
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while s and operators[s[-1]] >= operators[x]:
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result.append(s.pop())
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s.append(x)
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else:
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result.append(x)
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while s:
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result.append(s.pop())
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return result
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def evaluate(xs):
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s = []
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for x in xs:
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print(s, x)
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if x == '*':
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s.append(s.pop() * s.pop())
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elif x == '+':
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s.append(s.pop() + s.pop())
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else:
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s.append(x)
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print(s)
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return s[-1]
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print(evaluate(postfix(tokenize("12+3*10"))))
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