66 lines
1.8 KiB
Python
66 lines
1.8 KiB
Python
# this snippet was taken from this link
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# http://code.activestate.com/recipes/576694/
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from collections.abc import MutableSet
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class OrderedSet(MutableSet):
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def __init__(self, iterable=None):
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self.end = end = []
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end += [None, end, end] # sentinel
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# node for doubly linked list
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self.map = {} # key --> [key, prev, next]
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if iterable is not None:
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self |= iterable
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def __len__(self):
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return len(self.map)
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def __contains__(self, key):
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return key in self.map
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def add(self, key):
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if key not in self.map:
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end = self.end
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curr = end[1]
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curr[2] = end[1] = self.map[key] = [key, curr, end]
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def intersection(self, set_b):
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return OrderedSet([item for item in self if item in set_b])
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def discard(self, key):
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if key in self.map:
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key, prev, next = self.map.pop(key)
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prev[2] = next
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next[1] = prev
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def __iter__(self):
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end = self.end
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curr = end[2]
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while curr is not end:
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yield curr[0]
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curr = curr[2]
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def __reversed__(self):
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end = self.end
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curr = end[1]
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while curr is not end:
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yield curr[0]
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curr = curr[1]
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def pop(self, last=True):
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if not self:
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raise KeyError("set is empty")
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key = self.end[1][0] if last else self.end[2][0]
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self.discard(key)
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return key
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def __repr__(self):
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if not self:
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return f"{self.__class__.__name__}()"
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return f"{self.__class__.__name__}({list(self)!r})"
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def __eq__(self, other):
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if isinstance(other, OrderedSet):
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return len(self) == len(other) and list(self) == list(other)
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return set(self) == set(other)
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