一、成品代码

#include<iostream>
using namespace std;

#define inf -1

class Graph {
private:
	int vertices;
	int** edges;
public:
	Graph(int vertices);
	~Graph();
	void addEdge(int u, int v, int w);//代表往这个图中添加一条从u到v的边，边的权为w
	void printGraph();
};

//构造函数
Graph::Graph(int vertices) {
	this->vertices = vertices;//顶点个数
	edges = new int* [vertices];//二维数组，一个指针数组，每个指针指向一个数组
	//初始化数组
	for (int i = 0; i < vertices; i++) {
		edges[i] = new int[vertices];
		for (int j = 0; j < vertices; j++) {
			edges[i][j] = inf;
		}
	}
}

//析构函数
Graph::~Graph() {
	for (int i = 0; i < vertices; i++) {
		delete[] edges[i];
	}
	delete[] edges;
}

void Graph::addEdge(int u, int v, int w) {
	edges[u][v] = w;
}
void Graph::printGraph() {
	for (int i = 0; i < vertices; i++) {
		for (int j = 0; j < vertices; j++) {
			cout << edges[i][j] << " ";
		}
		cout << endl;
	}
}

int main() {
	int vertices = 5;
	Graph graph(vertices);

	graph.addEdge(0, 1, 1);
	graph.addEdge(0, 2, 3);
	graph.addEdge(1, 2, 2);
	graph.addEdge(2, 3, 7);
	graph.addEdge(3, 4, 9);
	graph.addEdge(4, 0, 4);
	graph.addEdge(4, 2, 5);

	graph.printGraph();
	return 0;
}

二、构造过程

（1）我们的目标是构造一个图，一个图需要由顶点和线构成，图可以由邻接矩阵来表示，矩阵我们又可以由二维数组表示。因此我们的类需要有两个元素，顶点个数和一个二维数组。我们还需要连线的方法和打印图的方法。其中连线的方法我们需要知道线是从谁连向谁，权重是多少。构造函数时需要知道有多少个顶点，构造出空的图。

#include<iostream>
using namespace std;

class Graph {
	int vertices;
	int** edges;
	Graph(int vertices);
	~Graph();
	void addGraph(int u,int v,int w);
	void printGraph();
};

（2）我们先实现构造函数的方法，我们需要或的一个vertices大小的指针数组，数组中的每个元素是一个vertices大小的数组。并将数组中每个元素初始化为空（指定任意不可能取到的值即可）。

#include<iostream>
using namespace std;

#define inf -1
class Graph {
	int vertices;
	int** edges;
	Graph(int vertices);
	~Graph();
	void addGraph(int u,int v,int w);
	void printGraph();
};

Graph::Graph(int vertices) {
	this->vertices = vertices;
	edges = new int* [vertices];
	for (int i = 0; i < vertices; i++) {
		edges[i] = new int[vertices];
		for (int j = 0; j < vertices; j++) {
			edges[i][j] = inf;
		}
	}
}
Graph::~Graph() {

}
void Graph::addGraph(int u, int v, int w) {

}
void Graph::printGraph() {

}

（3）析构函数则是遍历指针数组，将每个元素一一删除，再将指针数组删除

#include<iostream>
using namespace std;

#define inf -1
class Graph {
	int vertices;
	int** edges;
	Graph(int vertices);
	~Graph();
	void addGraph(int u,int v,int w);
	void printGraph();
};

Graph::Graph(int vertices) {
	this->vertices = vertices;
	edges = new int* [vertices];
	for (int i = 0; i < vertices; i++) {
		edges[i] = new int[vertices];
		for (int j = 0; j < vertices; j++) {
			edges[i][j] = inf;
		}
	}
}
Graph::~Graph() {
	for (int i = 0; i < vertices; i++) {
		delete[]edges[i];
	}
	delete edges;
}
void Graph::addGraph(int u, int v, int w) {

}
void Graph::printGraph() {

}

（4）连线直接给二维数组对应索引赋值即可

#include<iostream>
using namespace std;

#define inf -1
class Graph {
	int vertices;
	int** edges;
	Graph(int vertices);
	~Graph();
	void addGraph(int u,int v,int w);
	void printGraph();
};

Graph::Graph(int vertices) {
	this->vertices = vertices;
	edges = new int* [vertices];
	for (int i = 0; i < vertices; i++) {
		edges[i] = new int[vertices];
		for (int j = 0; j < vertices; j++) {
			edges[i][j] = inf;
		}
	}
}
Graph::~Graph() {
	for (int i = 0; i < vertices; i++) {
		delete[]edges[i];
	}
	delete edges;
}
void Graph::addGraph(int u, int v, int w) {
	edges[u][v] = w;
}

（5）打印就是简单的遍历即可

#include<iostream>
using namespace std;

#define inf -1
class Graph {
	int vertices;
	int** edges;
	Graph(int vertices);
	~Graph();
	void addGraph(int u,int v,int w);
	void printGraph();
};

Graph::Graph(int vertices) {
	this->vertices = vertices;
	edges = new int* [vertices];
	for (int i = 0; i < vertices; i++) {
		edges[i] = new int[vertices];
		for (int j = 0; j < vertices; j++) {
			edges[i][j] = inf;
		}
	}
}
Graph::~Graph() {
	for (int i = 0; i < vertices; i++) {
		delete[]edges[i];
	}
	delete edges;
}
void Graph::addGraph(int u, int v, int w) {
	edges[u][v] = w;
}
void Graph::printGraph() {
	for (int i = 0; i < vertices; i++) {
		for (int j = 0; j < vertices; j++) {
			cout << edges[i][j] << " ";
		}
		cout << endl;
	}
}