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22 lines
483 B
22 lines
483 B
class Stack:
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class StackElem:
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def __init__(self, elt, prec):
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self.elt = elt
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self.prec = prec
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def __init__(self, elts=[]):
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self.first = None
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for e in elts:
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self.add(e)
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def add(self, e):
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se = self.StackElem(e, self.first)
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self.first = se
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def pop(self):
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e = self.first.elt
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self.first = self.first.prec
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return e
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def empty(self):
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return self.first is None
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