/*
* Disjoint-set data structure - Library header (C)
*
* Copyright (c) 2021 Project Nayuki. (MIT License)
* https://www.nayuki.io/page/disjoint-set-data-structure
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
* - The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* - The Software is provided "as is", without warranty of any kind, express or
* implied, including but not limited to the warranties of merchantability,
* fitness for a particular purpose and noninfringement. In no event shall the
* authors or copyright holders be liable for any claim, damages or other
* liability, whether in an action of contract, tort or otherwise, arising from,
* out of or in connection with the Software or the use or other dealings in the
* Software.
*/
#pragma once
#include
#include
/*---- Data structure types ----*/
// Private structure, for internal use only.
struct DisjointSetNode {
// The index of the parent element. An element is a representative
// iff its parent is itself. Mutable due to path compression.
size_t parent;
// Positive number if the element is a representative, otherwise zero.
size_t size;
};
// Public structure.
struct DisjointSet {
// The number of elements among the set of disjoint sets; this was the number passed
// into the constructor and is constant for the lifetime of the object. The various
// functions require the argument elemIndex to satisfy 0 <= elemIndex < numElements.
// Publicly readable and never writable.
size_t numElements;
// The current number of disjoint sets overall. This number decreases monotonically as time
// progresses; each call to mergeSets() either decrements the number by one or leaves it
// unchanged. 0 <= numSets <= numElements. Publicly readable but only privately writable.
size_t numSets;
// The internal nodes representing the disjoint-set data structure.
// Only privately readable and writable. Flexible array member (C99 and above, unsupported in C++).
struct DisjointSetNode nodes[];
};
/*---- Constructors/destructors ----*/
// Constructs a new set containing the given number of singleton sets.
// For example, DisjointSet_init(3) --> {{0}, {1}, {2}}.
struct DisjointSet *DisjointSet_init(size_t numElems);
// Releases the memory for a disjoint-set data structure object. The argument can be NULL.
// Do not attempt to call free() on the pointer, because there may be internal structures and other
// implementation details. This function returns NULL to facilitate this code idiom: ds = destroy(ds);
struct DisjointSet *DisjointSet_destroy(struct DisjointSet this[static 1]);
/*---- Object methods ----*/
// Note that most methods take a (struct DisjointSet *) instead of a (const struct DisjointSet *)
// because they use the private function getRepr() which performs path compression. Path compression
// mutates and optimizes the data structure, but without affecting the answers returned.
// Returns the size of the set that the given element is a member of. 1 <= result <= numElements.
size_t DisjointSet_getSizeOfSet(struct DisjointSet this[static 1], size_t elemIndex);
// Tests whether the given two elements are members of the same set. Note that the arguments are orderless.
bool DisjointSet_areInSameSet(struct DisjointSet this[static 1], size_t elemIndex0, size_t elemIndex1);
// Merges together the sets that the given two elements belong to. This method is also known as "union" in the literature.
// If the two elements belong to different sets, then the two sets are merged and the method returns true.
// Otherwise they belong in the same set, nothing is changed and the method returns false. Note that the arguments are orderless.
bool DisjointSet_mergeSets(struct DisjointSet this[static 1], size_t elemIndex0, size_t elemIndex1);
// For unit tests. This detects many but not all invalid data structures, failing an assert() if
// a structural invariant is known to be violated. This always returns silently on a valid object.
void DisjointSet_checkStructure(const struct DisjointSet this[static 1]);