Kruskal 法
(include/emthrm/graph/kruskal.hpp)

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• Last update: 2023-02-25 16:35:06+09:00
• Include: #include "emthrm/graph/kruskal.hpp"

最小全域木 (minimum spanning tree)

時間計算量

$O(\lvert E \rvert \log{\lvert V \rvert})$

仕様

Prim 法

名前	戻り値	要件
template <typename CostType> CostType prim(const std::vector<std::vector<Edge<CostType>>>& graph, const int root = 0);	根を $\mathrm{root}$ とするグラフ $\mathrm{graph}$ の最小全域木のコスト	$\mathrm{graph}$ は双方向の辺の情報をもつ。

Kruskal 法

名前	戻り値	備考
template <typename CostType> CostType kruskal(const std::vector<std::vector<Edge<CostType>>>& graph);	グラフ $\mathrm{graph}$ の最小全域木のコスト	$\mathrm{graph}$ には単方向の辺の情報のみでよい。

参考文献

Prim 法

• Robert C. Prim: Shortest connection networks and some generalizations, The Bell System Technical Journal, Vol. 36, No. 6, pp. 1389–1401 (1957). https://doi.org/10.1002/j.1538-7305.1957.tb01515.x
• http://www.prefield.com/algorithm/graph/prim.html

Kruskal 法

• Joseph B. Kruskal: On the shortest spanning subtree of a graph and the traveling salesman problem, Proceedings of the American Mathematical Society, Vol. 7, pp. 48–50 (1956). https://doi.org/10.1090/S0002-9939-1956-0078686-7
• https://github.com/spaghetti-source/algorithm/blob/64d34fb9b940a3e933cf36c4dd26b7457b42f50b/graph/kruskal.cc

TODO

• https://www.slideshare.net/tmaehara/ss-17402143
• https://twitter.com/noshi91/status/1482583425421029376
• ブルーフカ法 (Borůvka’s algorithm)
  • https://ja.wikipedia.org/wiki/%E3%83%96%E3%83%AB%E3%83%BC%E3%83%95%E3%82%AB%E6%B3%95
  • http://spinda2.blog48.fc2.com/blog-entry-560.html
  • https://inzkyk.github.io/algorithms/minimum_spanning_trees/boruvka_algorithms/
  • https://twitter.com/yamerarenaku/status/1166349080022462465
  • https://ei1333.github.io/luzhiled/snippets/graph/boruvka.html
  • https://lumakernel.github.io/ecasdqina/graph/boruvka
• Fibonacchi heap を用いた Prim 法の高速化
  • https://github.com/ei1333/library/blob/master/graph/prim-fibonacchi-heap.cpp
• Euclidean minimum spanning tree
  • https://en.wikipedia.org/wiki/Euclidean_minimum_spanning_tree
  • https://www.slideshare.net/maroonrk/ss-65378126
  • http://tokoharuland.hateblo.jp/entry/2018/04/01/155743
  • https://github.com/beet-aizu/library/blob/master/graph/voronoiminimumspanningtree.cpp
• 最小シュタイナー木
  • https://ja.wikipedia.org/wiki/%E3%82%B7%E3%83%A5%E3%82%BF%E3%82%A4%E3%83%8A%E3%83%BC%E6%9C%A8
  • https://www.slideshare.net/wata_orz/ss-12131479
  • http://www.prefield.com/algorithm/dp/steiner_tree.html
  • http://monyone.github.io/teihen_library/#MinimumSteinerTree
  • https://sotanishy.github.io/cp-library-cpp/graph/minimum_steiner_tree.hpp
• 最小全域有向木
  • https://37zigen.com/gabow-galil-spencer-tarjan/
  • https://noshi91.github.io/algorithm-encyclopedia/chu-liu-edmonds
  • http://joisino.hatenablog.com/entry/2017/01/11/230141
  • https://ark4rk.hatenablog.com/entry/2017/09/15/011937
  • https://twitter.com/nuo_chocorusk/status/1187055311422574593
  • https://twitter.com/yamerarenaku/status/1187065174529691648
  • https://ei1333.github.io/algorithm/chu-liu-edmond.html
  • https://ei1333.github.io/luzhiled/snippets/graph/chu-liu-edmond.html
  • https://github.com/beet-aizu/library/blob/master/graph/arborescence_edmond.cpp
  • https://github.com/beet-aizu/library/blob/master/graph/arborescence_tarjan.cpp
  • https://lumakernel.github.io/ecasdqina/graph/MinimumSpanningArborescence
  • http://www.prefield.com/algorithm/graph/chu_liu_edmonds.html
  • https://github.com/spaghetti-source/algorithm/blob/master/graph/arborescence.cc
  • https://github.com/spaghetti-source/algorithm/blob/master/graph/arborescence2.cc
  • https://github.com/primenumber/ProconLib/blob/master/Graph/MinimumArborescence.cpp
  • https://gist.github.com/tjkendev/231897301fde67d4a81f51c3f0873936
  • https://sotanishy.github.io/cp-library-cpp/graph/minimum_spanning_arborescence.cpp
  • https://onlinejudge.u-aizu.ac.jp/courses/library/5/GRL/2/GRL_2_B
  • https://judge.yosupo.jp/problem/directedmst
• minimum diameter spanning tree
  • http://www.prefield.com/algorithm/graph/minimum_diameter_spanning_tree.html
  • https://github.com/spaghetti-source/algorithm/blob/master/graph/kariv_hakimi.cc

Submissons

• Prim 法
• Kruskal 法

Depends on

• union-find (include/emthrm/data_structure/union-find/union-find.hpp)
• 辺 (include/emthrm/graph/edge.hpp)

Verified with

• グラフ/Kruskal 法 (test/graph/kruskal.test.cpp)

Code

#ifndef EMTHRM_GRAPH_KRUSKAL_HPP_
#define EMTHRM_GRAPH_KRUSKAL_HPP_

#include <algorithm>
#include <ranges>
#include <vector>

#include "emthrm/data_structure/union-find/union-find.hpp"
#include "emthrm/graph/edge.hpp"

namespace emthrm {

template <typename CostType>
CostType kruskal(const std::vector<std::vector<Edge<CostType>>>& graph) {
  const int n = graph.size();
  const auto jv = graph | std::views::join;
  std::vector<Edge<CostType>> edges(jv.begin(), jv.end());
  std::ranges::sort(edges);
  CostType res = 0;
  UnionFind uf(n);
  for (const Edge<CostType>& e : edges) {
    if (uf.unite(e.src, e.dst)) res += e.cost;
  }
  return res;
}

}  // namespace emthrm

#endif  // EMTHRM_GRAPH_KRUSKAL_HPP_

#line 1 "include/emthrm/graph/kruskal.hpp"



#include <algorithm>
#include <ranges>
#include <vector>

#line 1 "include/emthrm/data_structure/union-find/union-find.hpp"



#include <utility>
#line 6 "include/emthrm/data_structure/union-find/union-find.hpp"

namespace emthrm {

struct UnionFind {
  explicit UnionFind(const int n) : data(n, -1) {}

  int root(const int ver) {
    return data[ver] < 0 ? ver : data[ver] = root(data[ver]);
  }

  bool unite(int u, int v) {
    u = root(u);
    v = root(v);
    if (u == v) return false;
    if (data[u] > data[v]) std::swap(u, v);
    data[u] += data[v];
    data[v] = u;
    return true;
  }

  bool is_same(const int u, const int v) { return root(u) == root(v); }

  int size(const int ver) { return -data[root(ver)]; }

 private:
  std::vector<int> data;
};

}  // namespace emthrm


#line 1 "include/emthrm/graph/edge.hpp"
/**
 * @title 辺
 */

#ifndef EMTHRM_GRAPH_EDGE_HPP_
#define EMTHRM_GRAPH_EDGE_HPP_

#include <compare>

namespace emthrm {

template <typename CostType>
struct Edge {
  CostType cost;
  int src, dst;

  explicit Edge(const int src, const int dst, const CostType cost = 0)
      : cost(cost), src(src), dst(dst) {}

  auto operator<=>(const Edge& x) const = default;
};

}  // namespace emthrm

#endif  // EMTHRM_GRAPH_EDGE_HPP_
#line 10 "include/emthrm/graph/kruskal.hpp"

namespace emthrm {

template <typename CostType>
CostType kruskal(const std::vector<std::vector<Edge<CostType>>>& graph) {
  const int n = graph.size();
  const auto jv = graph | std::views::join;
  std::vector<Edge<CostType>> edges(jv.begin(), jv.end());
  std::ranges::sort(edges);
  CostType res = 0;
  UnionFind uf(n);
  for (const Edge<CostType>& e : edges) {
    if (uf.unite(e.src, e.dst)) res += e.cost;
  }
  return res;
}

}  // namespace emthrm

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