GreedySetCover.cpp

Author: lxylxy123456

GreedySetCover.cpp

@@ -0,0 +1,104 @@
+//  
+//  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_GreedySetCover
+#endif
+
+#ifndef FUNC_GreedySetCover
+#define FUNC_GreedySetCover
+
+#include <cassert>
+#include <iomanip>
+#include <set>
+#include "utils.h"
+
+#define set_T typename std::set<T>
+
+template <typename T>
+std::set<size_t> GreedySetCover(set_T& X, std::vector<set_T>& F) {
+	size_t U_size = X.size(); 
+	std::set<size_t> e; 
+	std::vector<set_T> FU = F; 
+	while (U_size) {
+		size_t s, s_size = 0; 
+		for (size_t i = 0; i < FU.size(); i++) {
+			size_t i_size = FU[i].size(); 
+			if (s_size < i_size) {
+				s = i; 
+				s_size = i_size; 
+			}
+		}
+		assert(s_size); 
+		for (auto i = FU[s].begin(); i != FU[s].end(); i++) {
+			U_size--; 
+			for (size_t j = 0; j < FU.size(); j++)
+				if (j != s)
+					FU[j].erase(*i); 
+		}
+		FU[s].clear(); 
+		e.insert(s); 
+	}
+	return e; 
+}
+#endif
+
+#ifdef MAIN_GreedySetCover
+int main(int argc, char *argv[]) {
+	const size_t n = get_argv(argc, argv, 1, 10); 
+	const size_t m = get_argv(argc, argv, 2, 10); 
+	const size_t l = get_argv(argc, argv, 2, 20); 
+	using T = size_t; 
+	set_T X; 
+	std::vector<set_T> F; 
+	for (size_t i = 0; i < n; i++)
+		X.insert(i); 
+    std::random_device rd; 
+    std::uniform_int_distribution<T> d1(0, n * m); 
+	for (size_t i = 0; i < m; i++) {
+		set_T s; 
+		for (size_t j = 0; j < n; j++)
+			if (d1(rd) < l)
+				s.insert(j); 
+		F.push_back(s); 
+	}
+    std::uniform_int_distribution<T> d2(0, m - 1); 
+    for (size_t i = 0; i < n; i++)
+    	F[d2(rd)].insert(i); 
+    std::uniform_int_distribution<T> d3(0, n - 1); 
+    for (size_t i = 0; i < m; i++)
+    	F[i].insert(d3(rd)); 
+    std::set<size_t> ans = GreedySetCover(X, F); 
+    for (size_t i = 0; i < m; i++) {
+    	if (ans.find(i) != ans.end())
+	    	std::cout << "+ "; 
+	    else
+	    	std::cout << "  "; 
+	    for (size_t j = 0; j < n; j++) {
+	    	if (F[i].find(j) != F[i].end())
+	    		std::cout << std::setw(4) << j; 
+	    	else
+	    		std::cout << std::string(4, ' '); 
+	    }
+	    std::cout << std::endl; 
+    }
+	return 0; 
+}
+#endif
+

README.md

@@ -224,6 +224,7 @@
 | 33 | ClosestPairPoints.cpp		| Closest Pair Points					| 1043 |
 | 35 | ApproxVertexCover.cpp		| Approx Vertex Cover					| 1109 |
 | 35 | ApproxTSPTour.cpp			| Approx TSP Tour						| 1112 |
+| 35 | GreedySetCover.cpp			| Greedy Set Cover						| 1119 |
 
 # Supplementary Files
 * `utils.h`: Utils