ApproxTSPTour.cpp

Author: lxylxy123456

ApproxTSPTour.cpp

@@ -0,0 +1,96 @@
+//  
+//  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_ApproxTSPTour
+#endif
+
+#ifndef FUNC_ApproxTSPTour
+#define FUNC_ApproxTSPTour
+
+#include "utils.h"
+
+#include "MST.cpp"
+#include "SegmentsIntersect.cpp"
+
+template <typename GT, typename T>
+void TreeWalk(GT& G, T current, T* last, std::vector<T>& H) {
+	H.push_back(current); 
+	for (auto i = G.edges_from(current); !i.end(); i++)
+		if (!last || i.d() != *last)
+			TreeWalk(G, i.d(), &current, H); 
+}
+
+template <typename GT, typename T, typename WT>
+void ApproxTSPTour(GT& G, umap_WT& c, std::vector<T>& H) {
+	T r = *G.V.begin(); 
+	umap<T, MSTPrimInfo<T, WT>> MST_info; 
+	MSTPrim(G, c, r, MST_info); 
+	GT MST_Graph(false); 
+	for (auto i = G.V.begin(); i != G.V.end(); i++) {
+		const MSTPrimInfo<T, WT>& info = MST_info[*i]; 
+		if (!info.pi_nil)
+			MST_Graph.add_edge(*i, info.pi); 
+	}
+	H.reserve(G.V.size() + 1); 
+	TreeWalk<GT, T>(MST_Graph, r, nullptr, H); 
+	H.push_back(r); 
+}
+#endif
+
+#ifdef MAIN_ApproxTSPTour
+int main(int argc, char *argv[]) {
+	const size_t n = get_argv(argc, argv, 1, 200); 
+	const size_t m = get_argv(argc, argv, 2, 10); 
+	const bool dir = 0; 
+	std::vector<int> b; 
+	random_integers(b, -n, n, m * 2); 
+	using T = size_t; 
+	using WT = double; 
+	GraphAdjList<size_t> G(dir); 
+	umap_WT c; 
+	std::vector<Vector<T>> S; 
+	S.reserve(m); 
+	for (size_t i = 0; i < m; i++) {
+		S.push_back(Vector<T>(b[2 * i + 0], b[2 * i + 1])); 
+		for (size_t j = 0; j < i; j++) {
+			G.add_edge(i, j); 
+			c[Edge<T>(i, j, false)] = (S[i] - S[j]).Length(); 
+		}
+	}
+	std::vector<size_t> H; 
+	ApproxTSPTour(G, c, H); 
+	std::cout << "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>"
+				 << std::endl; 
+	std::cout << "<svg height=\"" << 2 * n << "\" width=\"" << 2 * n << "\">"
+				 << std::endl; 
+	std::cout << "\t<rect fill=\"#ffffff\" x=\"0\" y=\"0\" width=\"" << 2 * n
+				 << "\" height=\"" << 2 * n << "\"/>" << std::endl; 
+	std::cout << "\t<polygon stroke=\"#000000\" fill=\"#cccccc\" points=\""; 
+	for (auto i = H.begin(); i != H.end(); i++)
+		std::cout << n + S[*i].x + 1 << "," << n + S[*i].y + 1 << " "; 
+	std::cout << "\"/>" << std::endl; 
+	for (size_t i = 0; i < m; i++)
+		std::cout << "\t<circle cx=\"" << n + S[i].x + 1 << "\" cy=\""
+				 << n + S[i].y + 1 << "\" r=\"2\"/>" << std::endl; 
+	std::cout << "</svg>" << std::endl; 
+	return 0; 
+}
+#endif
+

README.md

@@ -223,6 +223,7 @@
 | 33 | JarvisMarch.cpp				| Jarvis March							| 1038 |
 | 33 | ClosestPairPoints.cpp		| Closest Pair Points					| 1043 |
 | 35 | ApproxVertexCover.cpp		| Approx Vertex Cover					| 1109 |
+| 35 | ApproxTSPTour.cpp			| Approx TSP Tour						| 1112 |
 
 # Supplementary Files
 * `utils.h`: Utils