C++ 图基础

1、分类

  • 无向图
  • 有向图
  • 无权图
  • 有权图

2、简单图

没有自环边与平行边

3、图的表示

邻接矩阵 适合稠密图(完全图)

// 稠密图 - 邻接矩阵
class DenseGraph {

private:
	int n, m;
	bool directed;
	vector<vector<bool>> g;
public:
	DenseGraph(int n, bool directed) {
		this->n = n;
		this->m = 0;
		this->directed = directed;
		for (int i = 0; i < n; i++)
			g.push_back(vector<bool>(n, false));
	}
	~DenseGraph() {
	}
	int V() { 
		return n; 
	}
	int E() { 
		return m; 
	}
	void addEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		if (hasEdge(v, w))
			return;
		g[v][w] = true;
		if (!directed)
			g[w][v] = true;
		m++;
	}
	bool hasEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		return g[v][w];
	}
};

邻接表 适合稀疏图

// 稀疏图 - 邻接表
class SparseGraph {
private:
	int n, m;
	bool directed;
	vector<vector<int>> g;
public:
	SparseGraph(int n, bool directed) {
		this->n = n;
		this->m = 0;
		this->directed = directed;
		for (int i = 0; i < n; i++)
			g.push_back(vector<int>());
	}
	~SparseGraph() {
	}
	int V() { 
		return n; 
	}
	int E() { 
		return m; 
	}
	void addEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		g[v].push_back(w);
		if (v != w && !directed)
			g[w].push_back(v);
		m++;
	}
	bool hasEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		for (int i = 0; i < g[v].size(); i++)
			if (g[v][i] == w)
				return true;
		return false;
	}
};

4、遍历邻边

封装迭代器

邻接表

class adjIterator {
	private:
		SparseGraph &G;
		int v;
		int index;
	public:
		adjIterator(SparseGraph &graph, int v) : G(graph) {
			this->v = v;
			this->index = 0;
		}
		int begin() {
			index = 0;
			if (G.g[v].size())
				return G.g[v][index];
			return -1;
		}
		int next() {
			index++;
			if (index < (int)G.g[v].size())
				return G.g[v][index];
			return -1;
		}
		bool end() {
			return index >= (int)G.g[v].size();
		}
	};

邻接矩阵

	class adjIterator {
	private:
		DenseGraph &G;
		int v;
		int index;
	public:
		adjIterator(DenseGraph &graph, int v) : G(graph) {
			this->v = v;
			this->index = -1;
		}
		int begin() {
			index = -1;
			return next();
		}
		int next() {
			for (index += 1; index < G.V(); index++)
				if (G.g[v][index])
					return index;
			return -1;
		}
		bool end() {
			return index >= G.V();
		}
	};

5、遍历测试

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
#include <cassert>
#include <ctime>
using namespace std;

// 稠密图 - 邻接矩阵
class DenseGraph {

private:
	int n, m;
	bool directed;
	vector<vector<bool>> g;
public:
	DenseGraph(int n, bool directed) {
		this->n = n;
		this->m = 0;
		this->directed = directed;
		for (int i = 0; i < n; i++)
			g.push_back(vector<bool>(n, false));
	}
	~DenseGraph() {
	}
	int V() { 
		return n; 
	}
	int E() { 
		return m; 
	}
	void addEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		if (hasEdge(v, w))
			return;
		g[v][w] = true;
		if (!directed)
			g[w][v] = true;
		m++;
	}
	bool hasEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		return g[v][w];
	}

	class adjIterator {
	private:
		DenseGraph &G;
		int v;
		int index;
	public:
		adjIterator(DenseGraph &graph, int v) : G(graph) {
			this->v = v;
			this->index = -1;
		}
		int begin() {
			index = -1;
			return next();
		}
		int next() {
			for (index += 1; index < G.V(); index++)
				if (G.g[v][index])
					return index;
			return -1;
		}
		bool end() {
			return index >= G.V();
		}
	};
};

// 稀疏图 - 邻接表
class SparseGraph {
private:
	int n, m;
	bool directed;
	vector<vector<int>> g;
public:
	SparseGraph(int n, bool directed) {
		this->n = n;
		this->m = 0;
		this->directed = directed;
		for (int i = 0; i < n; i++)
			g.push_back(vector<int>());
	}
	~SparseGraph() {
	}
	int V() { 
		return n; 
	}
	int E() { 
		return m; 
	}
	void addEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		g[v].push_back(w);
		if (v != w && !directed)
			g[w].push_back(v);
		m++;
	}
	bool hasEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		for (int i = 0; i < (int)g[v].size(); i++)
			if (g[v][i] == w)
				return true;
		return false;
	}

	class adjIterator {
	private:
		SparseGraph &G;
		int v;
		int index;
	public:
		adjIterator(SparseGraph &graph, int v) : G(graph) {
			this->v = v;
			this->index = 0;
		}
		int begin() {
			index = 0;
			if (G.g[v].size())
				return G.g[v][index];
			return -1;
		}
		int next() {
			index++;
			if (index < (int)G.g[v].size())
				return G.g[v][index];
			return -1;
		}
		bool end() {
			return index >= (int)G.g[v].size();
		}
	};
};





int main(void)
{
	int N = 20;
	int M = 100;
	srand((int)time(NULL));
	// Sparse Graph
	SparseGraph g1(N, false);
	for (int i = 0; i < M; i++) {
		int a = rand() % N;
		int b = rand() % N;
		g1.addEdge(a, b);
	}
	// O(E)
	for (int v = 0; v < N; v++) {
		cout << v << " : ";
		SparseGraph::adjIterator adj(g1, v);
		for (int w = adj.begin(); !adj.end(); w = adj.next())
			cout << w << " ";
		cout << endl;
	}
	cout << endl;

	// Dense Graph
	DenseGraph g2(N, false);
	for (int i = 0; i < M; i++) {
		int a = rand() % N;
		int b = rand() % N;
		g2.addEdge(a, b);
	}
	// O(V^2)
	for (int v = 0; v < N; v++) {
		cout << v << " : ";
		DenseGraph::adjIterator adj(g2, v);
		for (int w = adj.begin(); !adj.end(); w = adj.next())
			cout << w << " ";
		cout << endl;
	}

	system("pause");
	return 0;
}

6、读图

对txt文件进行读取,封装。

template <typename Graph>
class ReadGraph {

public:
	ReadGraph(Graph &graph, const string &filename) {

		ifstream file(filename);
		string line;
		int V, E;
		assert(file.is_open());
		assert(getline(file, line));
		stringstream ss(line);
		ss >> V >> E;
		assert(V == graph.V());
		for (int i = 0; i < E; i++) {
			assert(getline(file, line));
			stringstream ss(line);
			int a, b;
			ss >> a >> b;
			assert(a >= 0 && a < V);
			assert(b >= 0 && b < V);
			graph.addEdge(a, b);
		}
	}
};

测试

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <cassert>
#include <vector>
#include <ctime>
using namespace std;


// 稠密图 - 邻接矩阵
class DenseGraph {

private:
	int n, m;
	bool directed;
	vector<vector<bool>> g;
public:
	DenseGraph(int n, bool directed) {
		this->n = n;
		this->m = 0;
		this->directed = directed;
		for (int i = 0; i < n; i++)
			g.push_back(vector<bool>(n, false));
	}
	~DenseGraph() {
	}
	int V() {
		return n;
	}
	int E() {
		return m;
	}
	void addEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		if (hasEdge(v, w))
			return;
		g[v][w] = true;
		if (!directed)
			g[w][v] = true;
		m++;
	}
	bool hasEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		return g[v][w];
	}
	void show() {

		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++)
				cout << g[i][j] << "\t";
			cout << endl;
		}
	}

	class adjIterator {
	private:
		DenseGraph &G;
		int v;
		int index;
	public:
		adjIterator(DenseGraph &graph, int v) : G(graph) {
			this->v = v;
			this->index = -1;
		}
		int begin() {
			index = -1;
			return next();
		}
		int next() {
			for (index += 1; index < G.V(); index++)
				if (G.g[v][index])
					return index;
			return -1;
		}
		bool end() {
			return index >= G.V();
		}
	};
};

// 稀疏图 - 邻接表
class SparseGraph {
private:
	int n, m;
	bool directed;
	vector<vector<int>> g;
public:
	SparseGraph(int n, bool directed) {
		this->n = n;
		this->m = 0;
		this->directed = directed;
		for (int i = 0; i < n; i++)
			g.push_back(vector<int>());
	}
	~SparseGraph() {
	}
	int V() {
		return n;
	}
	int E() {
		return m;
	}
	void addEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		g[v].push_back(w);
		if (v != w && !directed)
			g[w].push_back(v);
		m++;
	}
	bool hasEdge(int v, int w) {
		assert(v >= 0 && v < n);
		assert(w >= 0 && w < n);
		for (int i = 0; i < (int)g[v].size(); i++)
			if (g[v][i] == w)
				return true;
		return false;
	}
	void show() {

		for (int i = 0; i < n; i++) {
			cout << "vertex " << i << ":\t";
			for (int j = 0; j < g[i].size(); j++)
				cout << g[i][j] << "\t";
			cout << endl;
		}
	}

	class adjIterator {
	private:
		SparseGraph &G;
		int v;
		int index;
	public:
		adjIterator(SparseGraph &graph, int v) : G(graph) {
			this->v = v;
			this->index = 0;
		}
		int begin() {
			index = 0;
			if (G.g[v].size())
				return G.g[v][index];
			return -1;
		}
		int next() {
			index++;
			if (index < (int)G.g[v].size())
				return G.g[v][index];
			return -1;
		}
		bool end() {
			return index >= (int)G.g[v].size();
		}
	};
};




template <typename Graph>
class ReadGraph {

public:
	ReadGraph(Graph &graph, const string &filename) {

		ifstream file(filename);
		string line;
		int V, E;
		assert(file.is_open());
		assert(getline(file, line));
		stringstream ss(line);
		ss >> V >> E;
		assert(V == graph.V());
		for (int i = 0; i < E; i++) {
			assert(getline(file, line));
			stringstream ss(line);
			int a, b;
			ss >> a >> b;
			assert(a >= 0 && a < V);
			assert(b >= 0 && b < V);
			graph.addEdge(a, b);
		}
	}
};


int main(void)
{
	string filename = "testG1.txt";

	SparseGraph g1(13, false);
	ReadGraph<SparseGraph> readGraph1(g1, filename);
	g1.show();
	cout << endl;

	DenseGraph g2(13, false);
	ReadGraph<DenseGraph> readGraph2(g2, filename);
	g2.show();

	system("pause");
	return 0;
}
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