拓扑排序（AOV）---判断图中是否有环---《数据结构》严蔚敏

// exam1.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <stack>
using namespace std;

#define MAXVEX 20

typedef struct ArcNode
{
	int adjvex;
	void* Info;
	struct ArcNode* nextarc;
}ArcNode;

typedef struct HeadNode
{
	int data;
	ArcNode* firstarc;
}HeadNode;

typedef struct ALGraph
{
	int arcnum;
	int vexnum;
	HeadNode vex[MAXVEX];
}ALGraph;


void InitALGraph(ALGraph& G)
{
	cout<<"please enter the number of the vertex:"<<endl;
	cin>>G.vexnum;

	G.arcnum=0;
	for(int i=1;i<G.vexnum+1;i++)
	{
		G.vex[i].data=i;
		G.vex[i].firstarc=NULL;
	}

	cout<<"please enter the Arc..."<<endl;
	cout<<"headnode tailnode"<<endl;
	int adj1,adj2;
	while(cin>>adj1>>adj2)
	{
		G.arcnum++;
		ArcNode* arc;
		arc=G.vex[adj1].firstarc;
		if(arc==NULL)
		{
			G.vex[adj1].firstarc=(ArcNode*)malloc(sizeof(ArcNode));
			arc=G.vex[adj1].firstarc;
			arc->adjvex=adj2;
			arc->nextarc=NULL;
		}
		else
		{
			while(arc->nextarc)
			{
				arc=arc->nextarc;
			}
			arc->nextarc=(ArcNode*)malloc(sizeof(ArcNode));
			arc->nextarc->adjvex=adj2;
			arc->nextarc->nextarc=NULL;
		}
	}

	for(int i=1;i<G.vexnum+1;i++)
	{
		cout<<"vextex"<<i<<"'s adjacent vertices are:";
		ArcNode* arc;
		arc=G.vex[i].firstarc;
		while(arc!=NULL)
		{
			cout<<arc->adjvex<<" ";
			arc=arc->nextarc;
		}
		cout<<endl;
	}
}

void CalIndegree(ALGraph G,int* indegree)
{
	for(int i=1;i<G.vexnum+1;i++)
	{
		ArcNode* arc;
		arc=G.vex[i].firstarc;
		while(arc!=NULL)
		{
			indegree[arc->adjvex]++;
			arc=arc->nextarc;
		}
	}
}

void TopologicalSort(ALGraph G)
{
	int *indegree=(int*)malloc(sizeof(int)*(G.vexnum+1));
	memset(indegree,sizeof(int)*(G.vexnum+1));

	CalIndegree(G,indegree);
	stack<int> s;

	for(int i=1;i<G.vexnum+1;i++)
	{
		if(indegree[i]==0)
		{
			s.push(i);
		}
	}

	cout<<"The topological sort of the graph is"<<endl;
	int count=0;
	while(!s.empty())
	{
		int i=s.top();
		s.pop();
		cout<<i<<" ";
		count++;

		ArcNode* arc;
		arc=G.vex[i].firstarc;;
		while(arc!=NULL)
		{
			if(--indegree[arc->adjvex]==0)
			{
				s.push(arc->adjvex);
			}
			arc=arc->nextarc;
		}
	}

	cout<<endl;
	if(count==G.vexnum)
	{
		cout<<"No loop in the graph..."<<endl;
	}

	return;
}

int main(void)
{
	ALGraph G;
	InitALGraph(G);	
	
	TopologicalSort(G);

	system("pause");
	return 0;
}

（编辑：李大同）

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