From 3a5ba7daf8759ce0a893bab994304e5f125972cf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Uhl=C3=ADk?= <jan@uhlik.me>
Date: Thu, 29 Mar 2018 21:04:15 +0200
Subject: [PATCH] Add Jarkni-Prim algorithm.
---
.../src/spanning_tree/JarnikPrim.cpp | 22 ++++
.../src/spanning_tree/JarnikPrim.hpp | 110 ++++++++++++++++++
2 files changed, 132 insertions(+)
create mode 100644 alib2graph_algo/src/spanning_tree/JarnikPrim.cpp
create mode 100644 alib2graph_algo/src/spanning_tree/JarnikPrim.hpp
diff --git a/alib2graph_algo/src/spanning_tree/JarnikPrim.cpp b/alib2graph_algo/src/spanning_tree/JarnikPrim.cpp
new file mode 100644
index 0000000000..db6d6ea828
--- /dev/null
+++ b/alib2graph_algo/src/spanning_tree/JarnikPrim.cpp
@@ -0,0 +1,22 @@
+// JarnikPrim.cpp
+//
+// Created on: 19. 03. 2018
+// Author: Jan Uhlik
+// Modified by:
+//
+// Copyright (c) 2017 Czech Technical University in Prague | Faculty of Information Technology. All rights reserved.
+// Git repository: https://gitlab.fit.cvut.cz/algorithms-library-toolkit/automata-library
+
+#include "JarnikPrim.hpp"
+
+#include <registration/AlgoRegistration.hpp>
+namespace {
+
+// ---------------------------------------------------------------------------------------------------------------------
+// uni-directional
+
+auto JarnikPrim1 = registration::AbstractRegister<spanning_tree::JarnikPrim,
+ graph::WeightedUndirectedGraph<>,
+ const graph::WeightedUndirectedGraph<> &,
+ const DefaultNodeType &>(spanning_tree::JarnikPrim::findSpanningTree);
+}
diff --git a/alib2graph_algo/src/spanning_tree/JarnikPrim.hpp b/alib2graph_algo/src/spanning_tree/JarnikPrim.hpp
new file mode 100644
index 0000000000..c2900eb003
--- /dev/null
+++ b/alib2graph_algo/src/spanning_tree/JarnikPrim.hpp
@@ -0,0 +1,110 @@
+// JarnikPrim.hpp
+//
+// Created on: 19. 03. 2018
+// Author: Jan Uhlik
+// Modified by:
+//
+// Copyright (c) 2017 Czech Technical University in Prague | Faculty of Information Technology. All rights reserved.
+// Git repository: https://gitlab.fit.cvut.cz/algorithms-library-toolkit/automata-library
+
+#ifndef ALIB2_JARNIKPRIM_HPP
+#define ALIB2_JARNIKPRIM_HPP
+
+#include <alib/pair>
+#include <alib/set>
+#include <alib/map>
+
+#include <common/SupportFunction.hpp>
+
+namespace spanning_tree {
+
+class JarnikPrim {
+// ---------------------------------------------------------------------------------------------------------------------
+ public:
+
+ template<typename TGraph, typename TNode>
+ static
+ TGraph
+ findSpanningTree(const TGraph &graph, const TNode &start);
+
+// =====================================================================================================================
+
+ private:
+
+ template<typename TNode, typename TWeight>
+ struct Data {
+ ext::set<ext::pair<TWeight, TNode>> queue; // priority queue
+ ext::map<TNode, TWeight> g; // distances (aka G score)
+ ext::map<TNode, TNode> p; // parents
+ };
+
+// ---------------------------------------------------------------------------------------------------------------------
+
+ template<typename TNode, typename TWeight>
+ inline static void init(JarnikPrim::Data<TNode, TWeight> &data, const TNode &start);
+
+};
+
+// =====================================================================================================================
+
+template<typename TGraph, typename TNode>
+TGraph JarnikPrim::findSpanningTree(const TGraph &graph, const TNode &start) {
+ using weight_type = typename TGraph::edge_type::weight_type;
+
+ TGraph res;
+ Data<TNode, weight_type> data;
+
+ // Init search
+ init(data, start);
+
+ while (!data.queue.empty()) {
+ TNode n = data.queue.begin()->second;
+ data.queue.erase(data.queue.begin());
+
+ // If not already in spanning tree add it
+ auto search = data.p.find(n);
+ if (search != data.p.end()) {
+ res.addEdge(search->second, n, data.g.at(n));
+ }
+
+ for (const auto &s_edge: graph.successorEdges(n)) {
+ const TNode &s = common::SupportFunction::other(s_edge, n); // successor
+
+ // Calculate new G score
+ weight_type gscore = s_edge.weight();
+
+ // Search if the node s was already visited
+ auto search_d = data.g.find(s);
+
+ // If not or the distance can be improve do relaxation
+ if (search_d == data.g.end() || search_d->second > gscore) {
+ // Search if the node s is in OPEN
+ auto search_q = data.queue.find(ext::make_pair(search_d->second, s));
+ if (search_q != data.queue.end()) {
+ // Erase node from priority queue
+ data.queue.erase(search_q);
+ }
+
+ data.g[s] = gscore;
+ data.p.insert_or_assign(s, n);
+ data.queue.insert(ext::make_pair(data.g[s], s));
+ }
+ }
+ }
+
+ return res;
+}
+
+// ---------------------------------------------------------------------------------------------------------------------
+
+template<typename TNode, typename TWeight>
+void JarnikPrim::init(JarnikPrim::Data<TNode, TWeight> &data, const TNode &start) {
+ data.g[start] = 0;
+ data.p.insert_or_assign(start, start);
+ data.queue.insert(ext::make_pair(data.g[start], start));
+}
+
+// ---------------------------------------------------------------------------------------------------------------------
+
+} // namespace spanning_tree
+#endif //ALIB2_JARNIKPRIM_HPP
--
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