wehub-resource-sync
65 lines
2.1 KiB
Python
65 lines
2.1 KiB
Python
# Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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class UnionFind:
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"""Union-find data structure.
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Union-find is a data structure that keeps track of a set of elements partitioned
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into a number of disjoint (non-overlapping) subsets.
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Reference:
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https://en.wikipedia.org/wiki/Disjoint-set_data_structure
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Args:
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elements(list): The initialize element list.
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"""
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def __init__(self, elements=None):
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self._parents = [] # index -> parent index
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self._index = {} # element -> index
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self._curr_idx = 0
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if not elements:
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elements = []
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for ele in elements:
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self._parents.append(self._curr_idx)
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self._index.update({ele: self._curr_idx})
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self._curr_idx += 1
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def find(self, x):
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# Find the root index of given element x,
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# execute the path compress while finding the root index
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if x not in self._index:
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return -1
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idx = self._index[x]
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while idx != self._parents[idx]:
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t = self._parents[idx]
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self._parents[idx] = self._parents[t]
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idx = t
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return idx
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def union(self, x, y):
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# Union two given element
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x_root = self.find(x)
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y_root = self.find(y)
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if x_root == y_root:
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return
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self._parents[x_root] = y_root
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def is_connected(self, x, y):
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# If two given elements have the same root index,
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# then they are connected.
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return self.find(x) == self.find(y)
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