ApproxVertexCover.cpp

Author: lxylxy123456

ApproxVertexCover.cpp

@@ -0,0 +1,68 @@
+//  
+//  algorithm - some algorithms in "Introduction to Algorithms", third edition
+//  Copyright (C) 2018  lxylxy123456
+//  
+//  This program is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU Affero General Public License as
+//  published by the Free Software Foundation, either version 3 of the
+//  License, or (at your option) any later version.
+//  
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU Affero General Public License for more details.
+//  
+//  You should have received a copy of the GNU Affero General Public License
+//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//  
+
+#ifndef MAIN
+#define MAIN
+#define MAIN_ApproxVertexCover
+#endif
+
+#ifndef FUNC_ApproxVertexCover
+#define FUNC_ApproxVertexCover
+
+#include "utils.h"
+
+#include "Graph.cpp"
+
+template <typename GT, typename T>
+void ApproxVertexCover(GT& G, uset<T>& C) {
+	uset<Edge<T>, EdgeHash<T>> E; 
+	for (auto i = G.all_edges(); !i.end(); i++)
+		E.insert(*i); 
+	while (E.begin() != E.end()) {
+		Edge<T> e = *E.begin(); 
+		const T &u = e.s, &v = e.d; 
+		C.insert(u); 
+		C.insert(v); 
+		for (auto i = G.edges_from(u); !i.end(); i++)
+			E.erase(*i); 
+		for (auto i = G.edges_from(v); !i.end(); i++)
+			E.erase(*i); 
+	}
+}
+#endif
+
+#ifdef MAIN_ApproxVertexCover
+int main(int argc, char *argv[]) {
+	const size_t v = get_argv(argc, argv, 1, 10); 
+	const size_t e = get_argv(argc, argv, 2, 20); 
+	const bool dir = 0; 
+	GraphAdjList<size_t> G(dir); 
+	random_graph(G, v, e); 
+	uset<size_t> ans; 
+	ApproxVertexCover(G, ans); 
+	auto f1 = [ans](size_t v) {
+		if (ans.find(v) != ans.end())
+			std::cout << " [color=green]"; 
+		return false; 
+	}; 
+	auto f2 = [](Edge<size_t>) mutable {}; 
+	graphviz(G, f1, f2); 
+	return 0; 
+}
+#endif
+

README.md

@@ -222,6 +222,7 @@
 | 33 | GrahamScan.cpp				| Graham Scan							| 1031 |
 | 33 | JarvisMarch.cpp				| Jarvis March							| 1038 |
 | 33 | ClosestPairPoints.cpp		| Closest Pair Points					| 1043 |
+| 35 | ApproxVertexCover.cpp		| Approx Vertex Cover					| 1109 |
 
 # Supplementary Files
 * `utils.h`: Utils