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