示例输入：

a b c d //每个顶点的名字 char型
(CTRL+Z) //标示输入结束
7 //有向图中弧的个数
0 1 //该数对代表从编号为0的顶点到编号为1的顶点之间有一条弧 0->1 下同
0 2 //a、b、c、d编号分别为0、1、2、3
2 0
2 3
3 0
3 1
3 2

示例输出：

有向图示例

head.h

#include<iostream>
#define MAX_VERTEX_NUM 20
using namespace std;

class ArcBox //弧
{
public:
	ArcBox();
	int tailvex, headvex;
	ArcBox *hlink, *tlink;
	char info;
};

ArcBox::ArcBox()
{
	tailvex = headvex = 0;
	hlink = tlink = NULL;
}

class VexNode //顶点
{
public:
	VexNode();
	char data;
	ArcBox *firstin, *firstout;
};

VexNode::VexNode()
{
	firstin = firstout = NULL;
}

class OlGraphMessage //十字链表相关
{
public:
	OlGraphMessage();
	VexNode xlist[MAX_VERTEX_NUM];
	int vexnum, arcnum;
};

OlGraphMessage::OlGraphMessage()
{
	vexnum = arcnum = 0;
}

class OLGRAPH
{
public:
	void OlGraphConstructor(); //建立十字链表
private:
	void GetVertex(); //得到顶点信息
	void GetArcNum(); //得到弧度数
	void CreatOl(); //根据顶点信息建立十字链表
	void OlPrinter(); //输出顶点信息
	OlGraphMessage ol;
};

void OLGRAPH::OlGraphConstructor()
{
	cout << "OlGraphConstructor Called !" << endl << endl;
	GetVertex(); //得到顶点信息
	GetArcNum(); //得到弧度数
	CreatOl(); //根据顶点信息建立十字链表
	OlPrinter(); //输出顶点信息
}

void OLGRAPH::GetVertex() //得到顶点信息
{
	cout << "GetVertex Called !" << endl << endl;
	cout << "Please Enter The Vertex" << endl << endl;
	while (cin >> ol.xlist[ol.vexnum].data)
		ol.vexnum++;
	cin.clear();
}

void OLGRAPH::GetArcNum() //得到弧度数
{
	cout << "GetArcNum Called !" << endl << endl;
	cout << "Please Enter The Number Of The Arc" << endl << endl;
	cin >> ol.arcnum;
}
void OLGRAPH::CreatOl() //根据顶点信息建立十字链表
{
	cout << "CreatOl Called !" << endl << endl;
	cout << "Please Input The ArcMessage :" << endl << endl;
	int a, b;
	ArcBox *insert, *p;
	while (ol.arcnum--)
	{
		cin >> a >> b;
		insert = new ArcBox;
		insert->headvex = a;
		insert->tailvex = b;
		p = ol.xlist[a].firstout;
		if (p == NULL)
		{
			ol.xlist[a].firstout = insert;
		}
		else
		{
			while (p->tlink != NULL)
				p = p->tlink;
			p->tlink = insert;
		}
		p = ol.xlist[b].firstin;
		if (p == NULL)
		{
			ol.xlist[b].firstin = insert;
		}
		else
		{
			while (p->hlink != NULL)
				p = p->hlink;
			p->hlink = insert;
		}
	}
	cout << "CreatOl Succeed !" << endl << endl;
}

void OLGRAPH::OlPrinter() //输出顶点信息
{
	cout << "OlPrinter Called !" << endl << endl;
	ArcBox *p;
	int od, id;
	for (int i = 0; i < ol.vexnum; i++)
	{
		cout << ol.xlist[i].data << " : " << endl; //输出顶点
		od = id = 0; //初始化出度和入度
		//求以该顶点为弧尾的弧
		p = ol.xlist[i].firstout;
		while (p != NULL)
		{
			cout << ol.xlist[p->headvex].data << "->"
					<< ol.xlist[p->tailvex].data << endl;
			p = p->tlink;
			od++;
		}
		cout << "OutDegree = " << od << endl;
		//求以该顶点为弧头的弧
		p = ol.xlist[i].firstin;
		while (p != NULL)
		{
			cout << ol.xlist[p->tailvex].data << "<-"
					<< ol.xlist[p->headvex].data << endl;
			p = p->hlink;
			id++;
		}
		cout << "InDegree = " << id << endl;
	}
}

main.cpp

#include"head.h"
int main()
{
	OLGRAPH ol;
	ol.OlGraphConstructor();
	system("pause");
}