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28 lines
578 B
Python
28 lines
578 B
Python
class Node(object):
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def __init__(self, data, next=None):
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self.data = data
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self.next = next
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class Stack(object):
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def __init__(self, top=None):
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self.top = top
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def push(self, data):
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node = Node(data, self.top)
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self.top = node
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def pop(self):
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if self.top is None:
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return None
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data = self.top.data
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self.top = self.top.next
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return data
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def peek(self):
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return self.top.data if self.top is not None else None
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def is_empty(self):
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return self.peek() is None |