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1f5134b368
* Create alternate_disjoint_set.py This code implements a disjoint set using Lists with added heuristics for efficiency Union by Rank Heuristic and Path Compression * Update alternate_disjoint_set.py Added typehints, doctests and some suggested variable name change * Update alternate_disjoint_set.py * Formatted with Black * More formatting * Formatting on line 28 * Error in Doctest * Doctest Update in alternate disjoint set * Fixed build error * Fixed doctest
69 lines
2.1 KiB
Python
69 lines
2.1 KiB
Python
"""
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Implements a disjoint set using Lists and some added heuristics for efficiency
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Union by Rank Heuristic and Path Compression
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"""
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class DisjointSet:
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def __init__(self, set_counts: list) -> None:
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"""
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Initialize with a list of the number of items in each set
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and with rank = 1 for each set
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"""
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self.set_counts = set_counts
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self.max_set = max(set_counts)
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num_sets = len(set_counts)
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self.ranks = [1] * num_sets
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self.parents = list(range(num_sets))
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def merge(self, src: int, dst: int) -> bool:
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"""
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Merge two sets together using Union by rank heuristic
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Return True if successful
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Merge two disjoint sets
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>>> A = DisjointSet([1, 1, 1])
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>>> A.merge(1, 2)
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True
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>>> A.merge(0, 2)
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True
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>>> A.merge(0, 1)
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False
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"""
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src_parent = self.get_parent(src)
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dst_parent = self.get_parent(dst)
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if src_parent == dst_parent:
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return False
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if self.ranks[dst_parent] >= self.ranks[src_parent]:
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self.set_counts[dst_parent] += self.set_counts[src_parent]
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self.set_counts[src_parent] = 0
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self.parents[src_parent] = dst_parent
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if self.ranks[dst_parent] == self.ranks[src_parent]:
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self.ranks[dst_parent] += 1
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joined_set_size = self.set_counts[dst_parent]
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else:
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self.set_counts[src_parent] += self.set_counts[dst_parent]
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self.set_counts[dst_parent] = 0
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self.parents[dst_parent] = src_parent
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joined_set_size = self.set_counts[src_parent]
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self.max_set = max(self.max_set, joined_set_size)
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return True
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def get_parent(self, disj_set: int) -> int:
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"""
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Find the Parent of a given set
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>>> A = DisjointSet([1, 1, 1])
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>>> A.merge(1, 2)
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True
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>>> A.get_parent(0)
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0
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>>> A.get_parent(1)
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2
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"""
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if self.parents[disj_set] == disj_set:
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return disj_set
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self.parents[disj_set] = self.get_parent(self.parents[disj_set])
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return self.parents[disj_set]
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