DFS.cpp

Author: lxylxy123456

BFS.cpp

@@ -109,11 +109,10 @@ int main(int argc, char *argv[]) {
 			std::cout << "d = INF"; 
 		else
 			std::cout << "d = " << i.d << "; pi = " << i.pi; 
-		std::cout << "\""; 
-		std::cout << "]"; 
+		std::cout << "\"]"; 
 		return true; 
 	}; 
-	auto f2 = [dir](Edge<size_t> e) {}; 
+	auto f2 = [](Edge<size_t> e) {}; 
 	graphviz(G, f1, f2); 
 	for (auto i = G.V.begin(); i != G.V.end(); i++) {
 		std::vector<size_t> ans; 

DFS.cpp

@@ -0,0 +1,175 @@
+//  
+//  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_DFS
+#endif
+
+#ifndef FUNC_DFS
+#define FUNC_DFS
+
+#include "utils.h"
+
+#include "Graph.cpp"
+
+const size_t INF = -1; 
+
+enum DFSColor { white, gray, black }; 
+
+enum DFSEdgeType { tree, back, forward, cross }; 
+
+template <typename T>
+class DFSInfo {
+	public:
+		DFSInfo(): color(white), d(INF), f(INF), pi_exist(false) {}
+		void set_color(DFSColor c, size_t& time) {
+			color = c; 
+			switch (color) {
+				case white: 
+					break; 
+				case gray: 
+					d = time++; 
+					break; 
+				case black: 
+					f = time++; 
+					break; 
+			}
+		}
+		void set_pi(T p) {
+			pi = p; 
+			pi_exist = true; 
+		}
+		enum DFSColor color; 
+		size_t d, f; 
+		T pi; 
+		bool pi_exist; 
+}; 
+
+std::ostream& operator<<(std::ostream& os, const DFSEdgeType& rhs) {
+	switch (rhs) {
+		case tree: 
+			return os << "T"; 
+		case back: 
+			return os << "B"; 
+		case forward: 
+			return os << "F"; 
+		case cross: 
+			return os << "C"; 
+		default: 
+			return os; 
+	}
+}
+
+template <typename T>
+bool is_ancestor(umap<T, DFSInfo<T>>& ans, T u, T v) {
+	if (u == v)
+		return true; 
+	DFSInfo<T>& info = ans[v]; 
+	if (info.pi_exist)
+		return is_ancestor(ans, u, info.pi); 
+	else
+		return false; 
+}
+
+template <typename GT, typename T, typename VT, typename ET>
+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; 
+				vinfo.set_pi(u); 
+				DFSVisit(G, ans, edge_ans, v, time); 
+				break; 
+			case gray: 
+				edge_ans[*i] = back; 
+				break; 
+			case black: 
+				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) {
+	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)
+		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]; 
+				}
+			}
+}
+#endif
+
+#ifdef MAIN_DFS
+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; 
+	umap<Edge<size_t>, DFSEdgeType, EdgeHash<size_t>> edge_inf; 
+	DFS(G, inf, edge_inf); 
+	auto f1 = [inf](size_t v) mutable {
+		DFSInfo<size_t>& i = inf[v]; 
+		std::cout << " ["; 
+		switch (i.color) {
+			case white: 
+				break; 
+			case black: 
+				std::cout << "color=black style=filled fontcolor=white "; 
+				break; 
+			case gray: 
+				std::cout << "color=gray style=filled "; 
+				break; 
+		}
+		std::cout << "label=\"" << v << "\\n"; 
+		std::cout << "d = " << i.d << "; f = " << i.f; 
+		if (i.pi_exist)
+			std::cout << "; pi = " << i.pi; 
+		std::cout << "\"]"; 
+		return true; 
+	}; 
+	auto f2 = [edge_inf](Edge<size_t> e) mutable {
+		std::cout << " [" << "label=\"" << edge_inf[e] << "\"]"; 
+	}; 
+	graphviz(G, f1, f2); 
+	return 0; 
+}
+#endif
+

Graph.cpp

@@ -41,10 +41,29 @@ class Edge {
 			else
 				return os << rhs.s << " -- " << rhs.d; 
 		}
+		bool operator==(const Edge& rhs) const {
+			return dir == rhs.dir && s == rhs.s && d == rhs.d; 
+		}
+		Edge<T> reverse() const {
+			return Edge<T>(d, s, dir); 
+		}
 		T s, d; 
 		bool dir; 
 }; 
 
+template <typename T>
+struct EdgeHash {
+    std::size_t operator()(Edge<T> t) const
+    {
+        size_t shift = sizeof(size_t) * 4; 
+        size_t a = std::hash<T>()(t.s); 
+        size_t b = std::hash<T>()(t.d); 
+        size_t B = b >> shift | b << shift; 
+        size_t C = t.dir << (shift - 1); 
+        return a ^ B ^ C; 
+    }
+};
+
 template <typename T>
 class EdgeIteratorAL1 {
 	public:
@@ -62,7 +81,7 @@ class EdgeIteratorAL1 {
 		}
 		void next() {
 			if (mbegin != mend)
-				while (sbegin == send || s() > d()) {
+				while (sbegin == send || (!dir && s() > d())) {
 					if (sbegin == send) {
 						mbegin++; 
 						if (mbegin == mend)
@@ -128,7 +147,7 @@ class EdgeIteratorAM1 {
 		}
 		void next() {
 			if (mbegin != mend)
-				while (sbegin == send || !sbegin->second || s() > d()) {
+				while (sbegin == send || !sbegin->second || !dir && s() > d()) {
 					if (sbegin == send) {
 						mbegin++; 
 						if (mbegin == mend)
@@ -287,12 +306,11 @@ void graphviz(T& G, F1 f1, F2 f2) {
 			std::cout << "; "; 
 	}
 	std::cout << std::endl; 
-	for (auto i = G.all_edges(); !i.end(); i++)
-		if (G.dir || i.s() < i.d()) {
-			std::cout << '\t' << *i; 
-			f2(*i); 
-			std::cout << "; " << std::endl; 
-		}
+	for (auto i = G.all_edges(); !i.end(); i++) {
+		std::cout << '\t' << *i; 
+		f2(*i); 
+		std::cout << "; " << std::endl; 
+	}
 	std::cout << "}" << std::endl; 
 }
 

README.md

@@ -146,6 +146,8 @@
 | 21 | DisjointSet.cpp				| Find Set								|  571 |
 | 22 | BFS.cpp						| BFS									|  595 |
 | 22 | BFS.cpp						| Print Path							|  601 |
+| 22 | DFS.cpp						| DFS									|  604 |
+| 22 | DFS.cpp						| DFS Visit								|  604 |
 
 # Supplementary Files
 * `utils.h`: Utils