抱歉老师，任务十八

#include<iostream>
using namespace std;
#define STACK_INIT_SIZE 100
#define STACKINCREMENT 10
#define MAX_VERTEX_NUM 20
typedef int InfoType;
typedef struct ArcNode {
	int adjvex;
	struct ArcNode *nextarc;
	InfoType weight;
}ArcNode;
typedef char VertexType;
typedef struct VNode {
	VertexType data;
	ArcNode *firstarc;
}VNode, AdjList[MAX_VERTEX_NUM];
typedef struct {
	AdjList vertices;
	int vexnum, arcnum;
}ALGraph;
typedef int ElemType;
typedef struct
{
	ElemType *base;
	ElemType *top;
	int stacksize;
}SqStack;
typedef int Status;
#define OK 1
#define ERROR 0
Status InitStack(SqStack &S)
{
	S.base = (ElemType *)malloc(STACK_INIT_SIZE * sizeof(ElemType));
	if (!S.base)
	{
		return ERROR;
	}
	S.top = S.base;
	S.stacksize = STACK_INIT_SIZE;
	return OK;
}
Status Push(SqStack &S, ElemType e)
{
	if (S.top - S.base >= S.stacksize)
	{
		S.base = (ElemType *)realloc(
			S.base, (S.stacksize + STACKINCREMENT) * sizeof(ElemType)
		);
		if (!S.base)
		{
			return ERROR;
		}
		S.top = S.base + S.stacksize;
		S.stacksize += STACKINCREMENT;
	}
	*S.top++ = e;
	return OK;
}
ElemType Pop(SqStack &S)
{
	if (S.base == S.top)
	{
		exit(1);
	}
	return *--S.top;
}
Status StackEmpty(SqStack S)
{
	if (S.base == S.top)
	{
		return 1;
	}
	return 0;
}
void CreateALGraph(ALGraph &G)
{
	cout << "顶点数目：";
	cin >> G.vexnum;
	cout << "弧边数目：";
	cin >> G.arcnum;
	for (int i = 0; i < G.vexnum; i++)
	{
		ArcNode *p_Tail;
		cout << "Seq " << i << "th:";
		cin >> G.vertices[i].data;
		G.vertices[i].firstarc = NULL;
		int _do;
		cout << "Do:";
		cin >> _do;
		if (!_do)
		{
			continue;
		}
		else
		{
			cout << "依次输入以" << G.vertices[i].data
				<< "为尾的弧的弧头与权值：" << endl;
			for (int j = 0; j < _do; j++)
			{
				ArcNode *p = (ArcNode *)malloc(sizeof(ArcNode));
				p->nextarc = NULL;
				cin >> p->adjvex;
				cin >> p->weight;
				if (!G.vertices[i].firstarc)
				{
					G.vertices[i].firstarc = p;
					p_Tail = p;
				}
				else
				{
					p_Tail->nextarc = p;
					p_Tail = p;
				}
			}
		}
	}
}
//ve初始化
int ve[MAX_VERTEX_NUM];
Status IfNecessaryPath(ALGraph G,SqStack &T)
{
	SqStack S;
	InitStack(S); InitStack(T);
	int Indegree[MAX_VERTEX_NUM] = {0};
	for (int i = 0; i < G.vexnum; i++)
	{
		if (!G.vertices[i].firstarc)
		{
			continue;
		}
		else
		{
			ArcNode *p = G.vertices[i].firstarc;
			while(p)
			{
				Indegree[p->adjvex]++;
				p = p->nextarc;
			}
		}
	}
	//0入度的节点入栈S
	for (int i = 0; i < G.vexnum; i++)
	{
		if (!Indegree[i])
		{
			Push(S,i);
		}
	}
	int count = 0;
	while (!StackEmpty(S))
	{
		int j = Pop(S);
		//j号顶点入栈T并且计数
		Push(T,j);
		count++;
		for (ArcNode *p = G.vertices[j].firstarc; p; p = p->nextarc)
		{
			if (--Indegree[p->adjvex] == 0)
			{
				Push(S, p->adjvex);
			}
			//MAX{  }
			if (ve[j] + p->weight > ve[p->adjvex])
			{
				ve[p->adjvex] = ve[j] + p->weight;
			}
		}
	}         
	if (count < G.vexnum)
	{
		return ERROR;
	}
	else
	{
		return OK;
	}
}
int vl[MAX_VERTEX_NUM];        
Status CalculatePath(ALGraph G)
{
	SqStack T;
	if (!IfNecessaryPath(G, T))
	{
		return ERROR;
	}
	//初始化事件最晚时间
	for (int i = 0; i < G.vexnum; i++)
	{
		vl[i] = ve[G.vexnum-1];
	}
	//按拓扑排序的逆序求顶点
	while (!StackEmpty(T))
	{
		int j = Pop(T);
		for (ArcNode *p = G.vertices[j].firstarc; p; p = p->nextarc)
		{
			int k = p->adjvex;
			int w = p->weight;
			//MIN{ }
			if (vl[k] - w < vl[j])
			{
				vl[j] = vl[k] - w;
			}
		}
 	}
	for (int j = 0; j < G.arcnum; j++)
	{
		for (ArcNode *p = G.vertices[j].firstarc; p; p = p->nextarc)
		{
			int k = p->adjvex, w = p->weight;
			int el = vl[k]-w, ee = ve[j];
			if (ee == el)
			{
				cout <<"<"<< G.vertices[j].data <<","
					<< G.vertices[k].data <<">"<< endl;
			}
		}
	}
}
int main(void)
{
	ALGraph G;
	CreateALGraph(G);
	CalculatePath(G);
	return 0;
}
#include<iostream>
using namespace std;
#define MAX_VERTEX_NUM 20
typedef int VRType;
typedef struct ArcCell {
	VRType adj;
	int *info;
}ArcCell,AdjMatrix[MAX_VERTEX_NUM][MAX_VERTEX_NUM];
typedef char VertexType;
typedef struct {
	VertexType vexs[MAX_VERTEX_NUM];
	AdjMatrix arcs;
	int vexnum, arcnum;
}MGraph;
int LocateVex(MGraph G, VertexType V)
{
	int i;
	G.vexs[G.vexnum] = V;
	for (i = 0; G.vexs[i] != V; i++);
	return i;
}
void CreateMGraph(MGraph &G)
{
	cout << "顶点：";
	cin >> G.vexnum;
	cout << "边数：";
	cin >> G.arcnum;
	cout << "构造顶点向量" << endl
		<< "请依次输入顶点：";
	for (int i = 0; i < G.vexnum; i++)
	{
		cin >> G.vexs[i];
	}
	for (int i = 0; i < G.vexnum; i++)
	{
		for (int j = 0; j < G.vexnum; j++)
		{
			G.arcs[i][j] = { 0,NULL };
		}
	}
	cout << "邻接矩阵赋值" << endl;
	for (int k = 0; k < G.arcnum; k++)
	{
		cout << "依次输入第" << k + 1 << "条边的弧尾、弧头、权值：";
		VertexType a, b; VRType w;
		cin >> a >> b >> w;
		int i = LocateVex(G, a);
		int j = LocateVex(G, b);
		G.arcs[i][j].adj = w;
	}
}
int SimpleLine(MGraph G, int m_i, int m_j, int k)
{
	//最终矩阵
	int Matrix[MAX_VERTEX_NUM][MAX_VERTEX_NUM];
	//过渡矩阵
	int TMatrix[MAX_VERTEX_NUM][MAX_VERTEX_NUM];
	cout << "单位矩阵：" << endl;
	for (int i = 0; i < G.vexnum; i++)
	{
		for (int j = 0; j < G.vexnum; j++)
		{
			if (i == j)
			{
				TMatrix[i][j] = 1;
			}
			else
			{
				TMatrix[i][j] = 0;
			}
			cout << TMatrix[i][j] << " ";
		}
		cout << endl;
	}
	for (int n = 0; n < k; n++)
	{
		//矩阵的相乘次数
		cout << n + 1 << "次：" << endl;
		for (int i = 0; i < G.vexnum; i++)
		{
			for (int j = 0; j < G.vexnum; j++)
			{
				int temp = 0;
				for (int k = 0; k < G.vexnum; k++)
				{
					temp += TMatrix[i][k] * G.arcs[k][j].adj;
				}
				Matrix[i][j] = temp;
				cout << Matrix[i][j] << " ";
			}
			cout << endl;
		}
		for (int i = 0; i < G.vexnum; i++)
		{
			for (int j = 0; j < G.vexnum; j++)
			{
				TMatrix[i][j] = Matrix[i][j];
			}
		}
		cout << endl;
	}
	return Matrix[m_i][m_j];
}
void IFHavePath(MGraph &G,int i,int j)
{
	for (int n = 1; n <= G.arcnum; n++)
	{
		if (SimpleLine(G, i, j, n))
		{
			cout << "长度为" << n << "的路径有。"<<endl;
		}
		else
		{
			cout << "长度为" << n << "的路径没有。"<<endl;
		}
	}
}
int main(void)
{
	MGraph G;
	CreateMGraph(G);
	int i, j; 
	cin >> i >> j;
	IFHavePath(G,i,j);
	return 0;
}