TopologicalSort.cpp

Author: lxylxy123456

DFS.cpp

@@ -76,8 +76,8 @@ std::ostream& operator<<(std::ostream& os, const DFSEdgeType& rhs) {
 	}
 }
 
-template <typename T>
-bool is_ancestor(umap<T, DFSInfo<T>>& ans, T u, T v) {
+template <typename T, typename VT>
+bool is_ancestor(VT& ans, T u, T v) {
 	if (u == v)
 		return true; 
 	DFSInfo<T>& info = ans[v]; 
@@ -88,50 +88,54 @@ bool is_ancestor(umap<T, DFSInfo<T>>& ans, T u, T v) {
 }
 
 template <typename GT, typename T, typename VT, typename ET>
-void DFSVisit(GT& G, VT& ans, ET& edge_ans, T u, size_t& time) {
+void DFSVisit(GT& G, VT& ans, ET edge_ans, T u, size_t& time) {
 	DFSInfo<T>& info = ans[u]; 
 	info.set_color(gray, time); 
 	for (auto i = G.edges_from(u); !i.end(); i++) {
 		T v = i.d(); 
 		DFSInfo<T>& vinfo = ans[v]; 
 		switch (vinfo.color) {
 			case white: 
-				edge_ans[*i] = tree; 
+				if (edge_ans)
+					(*edge_ans)[*i] = tree; 
 				vinfo.set_pi(u); 
 				DFSVisit(G, ans, edge_ans, v, time); 
 				break; 
 			case gray: 
-				edge_ans[*i] = back; 
+				if (edge_ans)
+					(*edge_ans)[*i] = back; 
 				break; 
 			case black: 
-				if (is_ancestor(ans, u, v))
-					edge_ans[*i] = forward; 
-				else
-					edge_ans[*i] = cross; 
+				if (edge_ans) {
+					if (is_ancestor(ans, u, v))
+						(*edge_ans)[*i] = forward; 
+					else
+						(*edge_ans)[*i] = cross; 
+				}
 				break; 
 		}
 	}
 	info.set_color(black, time); 
 }
 
 template <typename GT, typename VT, typename ET>
-void DFS(GT& G, VT& ans, ET& edge_ans) {
+void DFS(GT& G, VT& ans, ET edge_ans) {
 	using T = typename GT::vertix_type; 
 	for (auto i = G.V.begin(); i != G.V.end(); i++)
 		ans[*i] = DFSInfo<T>(); 
 	size_t time = 0; 
 	for (auto i = G.V.begin(); i != G.V.end(); i++)
 		if (ans[*i].color == white)
 			DFSVisit(G, ans, edge_ans, *i, time); 
-	if (!G.dir)
+	if (!G.dir && edge_ans) {
+		auto& ea = *edge_ans; 
 		for (auto i = G.all_edges(); !i.end(); i++)
 			if (i.s() < i.d()) {
 				Edge<T> j = (*i).reverse(); 
-				if (edge_ans[*i] != edge_ans[j]) {
-					edge_ans[j] = std::min(edge_ans[*i], edge_ans[j]); 
-					edge_ans[*i] = edge_ans[j]; 
-				}
+				if (ea[*i] != ea[j])
+					ea[*i] = ea[j] = std::min(ea[*i], ea[j]); 
 			}
+	}
 }
 #endif
 
@@ -144,7 +148,7 @@ int main(int argc, char *argv[]) {
 	random_graph(G, v, e); 
 	umap<size_t, DFSInfo<size_t>> inf; 
 	umap<Edge<size_t>, DFSEdgeType, EdgeHash<size_t>> edge_inf; 
-	DFS(G, inf, edge_inf); 
+	DFS(G, inf, &edge_inf); 
 	auto f1 = [inf](size_t v) mutable {
 		DFSInfo<size_t>& i = inf[v]; 
 		std::cout << " ["; 

README.md

@@ -148,6 +148,7 @@
 | 22 | BFS.cpp						| Print Path							|  601 |
 | 22 | DFS.cpp						| DFS									|  604 |
 | 22 | DFS.cpp						| DFS Visit								|  604 |
+| 22 | TopologicalSort.cpp			| Topological Sort						|  613 |
 
 # Supplementary Files
 * `utils.h`: Utils

TopologicalSort.cpp

@@ -0,0 +1,84 @@
+//  
+//  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_TopologicalSort
+#endif
+
+#ifndef FUNC_TopologicalSort
+#define FUNC_TopologicalSort
+
+#include <deque>
+#include "utils.h"
+
+#include "DFS.cpp"
+
+template <typename GT, typename T, typename VT>
+void DFSVisit_TS(GT& G, VT& inf, std::deque<T>& ans, T u, size_t& time) {
+	DFSInfo<T>& info = inf[u]; 
+	info.set_color(gray, time); 
+	for (auto i = G.edges_from(u); !i.end(); i++) {
+		T v = i.d(); 
+		DFSInfo<T>& vinfo = inf[v]; 
+		if (vinfo.color == white) {
+			vinfo.set_pi(u); 
+			DFSVisit_TS(G, inf, ans, v, time); 
+		}
+	}
+	info.set_color(black, time); 
+	ans.push_front(u); 
+}
+
+template <typename GT, typename VT, typename T>
+void DFS_TS(GT& G, VT& inf, std::deque<T>& ans) {
+	for (auto i = G.V.begin(); i != G.V.end(); i++)
+		inf[*i] = DFSInfo<T>(); 
+	size_t time = 0; 
+	for (auto i = G.V.begin(); i != G.V.end(); i++)
+		if (inf[*i].color == white)
+			DFSVisit_TS(G, inf, ans, *i, time); 
+}
+
+#endif
+
+#ifdef MAIN_TopologicalSort
+int main(int argc, char *argv[]) {
+	const size_t v = get_argv(argc, argv, 1, 5); 
+	const size_t e = get_argv(argc, argv, 2, 10); 
+	const bool dir = get_argv(argc, argv, 3, 0); 
+	GraphAdjList<size_t> G(dir); 
+	random_graph(G, v, e); 
+	umap<size_t, DFSInfo<size_t>> inf; 
+	std::deque<size_t> ans; 
+	DFS_TS(G, inf, ans); 
+	auto f1 = [inf](size_t v) mutable {
+		DFSInfo<size_t>& i = inf[v]; 
+		std::cout << " [label=\"" << v << "\\nd = " << i.d << "; f = " << i.f; 
+		if (i.pi_exist)
+			std::cout << "; pi = " << i.pi; 
+		std::cout << "\"]"; 
+		return true; 
+	}; 
+	auto f2 = [](Edge<size_t> e) mutable {}; 
+	graphviz(G, f1, f2); 
+	output_integers(ans); 
+	return 0; 
+}
+#endif
+