有向图

-Digraph.h 有向图的类

#ifndef __DIGRAPH_H__
#define __DIGRAPH_H__

#include <list>
#include <string>

class Digraph {
private:
	int vNum;	// 顶点数
	int eNum;	// 边数
	std::list<int>* adj;

public:
	Digraph(int vnum);
	~Digraph() { delete[] adj; }
	Digraph(const Digraph& G);

	int getV()const { return vNum; }
	int getE()const { return eNum; }
	std::list<int> getAdj(int v)const { 
		return adj[v];
	}
	Digraph reverse()const;
	std::string toString()const;

	void addEdge(int v, int w);
};

// constructor
Digraph::Digraph(int vnum) {
	vNum = vnum;
	eNum = 0;
	adj = new std::list<int>[vNum];
}

// copy constructor
Digraph::Digraph(const Digraph& G) {
	vNum = G.vNum;
	eNum = G.eNum;
	adj = new std::list<int>[vNum];
	for (int i = 0; i < vNum; ++i)
		adj[i] = G.adj[i];
}

// addEdge
void Digraph::addEdge(int v, int w) {
	adj[v].push_front(w);
	++eNum;
}

// reverse
Digraph Digraph::reverse()const {
	Digraph R(vNum);
	for (int v = 0; v < vNum; ++v) {
		for (int w : adj[v])
			R.addEdge(w, v);
	}
	return R;
}

// toString
std::string Digraph::toString()const {
	std::string s;
	for (int v = 0; v < vNum; ++v) {
		s += std::to_string(v) + ": ";
		for (int w : adj[v])
			s += std::to_string(w) + " ";
		s += "\n";
	}
	return s;
}

#endif

-DirectedDFS(DirectedDepthFirstSearch) 有向图深度优先搜索

判断图中点的可达性

#ifndef __DIRECTED_DFS_H__
#define __DIRECTED_DFS_H__

#include "Digraph.h"

// 解决单点可达性或者多点可达性
class DirectedDFS {
private:
	bool* marked;

public:
	DirectedDFS(const Digraph& G, int s);
	DirectedDFS(const Digraph& G, std::list<int> ilst);
	~DirectedDFS() { delete[] marked; }

	bool isMarked(int v)const { return marked[v]; }

private:
	void dfs(const Digraph& G, int v);
};

// constructor
DirectedDFS::DirectedDFS(const Digraph& G, int s) {
	marked = new bool[G.getV()];
	for (int i = 0; i < G.getV(); ++i)
		marked[i] = false;
	dfs(G, s);
}

// constructor
DirectedDFS::DirectedDFS(const Digraph& G, std::list<int> ilst) {
	marked = new bool[G.getV()];
	for (int i = 0; i < G.getV(); ++i)
		marked[i] = false;
	for (int v : ilst) {
		if (!marked[v])
			dfs(G, v);
	}
}

void DirectedDFS::dfs(const Digraph& G, int v) {
	marked[v] = true;
	for (int w : G.getAdj(v)) {
		if (!marked[w])
			dfs(G, w);
	}
}

#endif

-对上面两个类的测试 -main.cpp

#include "Digraph.h"
#include "DirectedDFS.h"
#include <iostream>
using namespace std;

int main()
{
	int vNum, eNum;
	cin >> vNum >> eNum;

	Digraph dg(vNum);
	int v, w;
	for (int i = 0; i < eNum; ++i) {
		cin >> v >> w;
		dg.addEdge(v, w);
	}

	cout << "ddfs1:" << endl;
	DirectedDFS ddfs1(dg, 1);
	for (int i = 0; i < vNum; ++i) {
		if (ddfs1.isMarked(i)) cout << i << " ";
	}

	cout << endl << "ddfs2:" << endl;
	DirectedDFS ddfs2(dg, 2);
	for (int i = 0; i < vNum; ++i) {
		if (ddfs2.isMarked(i)) cout << i << " ";
	}

	cout << endl << "ddfs3:" << endl;
	std::list<int> ilst;
	ilst.push_back(1); ilst.push_back(2); ilst.push_back(6);
	DirectedDFS ddfs3(dg, ilst); 
	for (int i = 0; i < vNum; ++i) {
		if (ddfs3.isMarked(i)) cout << i << " ";
	}

	return 0;
}