5.5拓扑排序

#include "stdafx.h"
#include <iostream.h>
#include <malloc.h>

int const vnum=6;
//单链表定义
typedef struct arcnode
{
    int adjvex;                                            //与其相连的下个结点的编号
    struct arcnode * nextarc;                            //指向下一个结点的指针
}ArcNodeTp;

//顶点定义
typedef struct vexnode
{
    int vertex;                                            //顶点的值
    int in;                                                //入度数量
    ArcNodeTp * firstarc;                                //指向的出度的单链表
}AdjList[vnum];

//图的定义
typedef struct graph
{
    AdjList adjlist;
    int vexnum,arcnum;
}GraphTp;

//建立一个新的结点
ArcNodeTp * CreateNewNode(int adjvex)
{
    ArcNodeTp * node=(ArcNodeTp *)malloc(sizeof(ArcNodeTp));
    node->adjvex=adjvex;
    node->nextarc=NULL;

    return node;
}

//建立P122的图5-17(a)
void CreateGraph(GraphTp & graph)
{
    graph.arcnum=7;
    graph.vexnum=vnum;

    ArcNodeTp * p=NULL;
    int index=0;
    //建立结点
    index=0;
    graph.adjlist[index].vertex=index;
    p=CreateNewNode(1);
        //修改头结点
    graph.adjlist[index].firstarc=p;
        //指向下一个结点
    p->nextarc=CreateNewNode(2);
    graph.adjlist[index].in=0;

    index=1;
    graph.adjlist[index].vertex=index;
    p=CreateNewNode(5);
    graph.adjlist[index].firstarc=p;
    graph.adjlist[index].in=1;

    index=2;
    graph.adjlist[index].vertex=index;
    p=CreateNewNode(5);
    graph.adjlist[index].firstarc=p;
    graph.adjlist[index].in=2;

    index=3;
    graph.adjlist[index].vertex=index;
    p=CreateNewNode(2);
    graph.adjlist[index].firstarc=p;
    p->nextarc=CreateNewNode(4);
    graph.adjlist[index].in=0;

    index=4;
    graph.adjlist[index].vertex=index;
    p=CreateNewNode(5);
    graph.adjlist[index].firstarc=p;
    graph.adjlist[index].in=1;

    index=5;
    graph.adjlist[index].vertex=index;
    graph.adjlist[index].firstarc=NULL;
    graph.adjlist[index].in=3;
    
}

void Top_Sort(GraphTp g)
{
    //用数组和一个变量模拟栈
    int stack[vnum];
    int top=0;
    
    int i=0;
    for(i=0;i<g.vexnum;i++)
    {
        if (g.adjlist[i].in==0)
        {
            stack[++top]=i;
        }
    }
    int count=0;
    while(top!=0)
    {
        int v=stack[top--];
        count++;
        cout<<"输出顶点:"<<g.adjlist[v].vertex<<endl;
        ArcNodeTp * p=g.adjlist[v].firstarc;
        //此循环目的是去掉此弧尾对应的顶点的边,实现的方法并非删除,则是将出度的对应的顶点的In-1
        while(p!=NULL)
        {
            //将弧头的入度数减一后,判断是否入度为0,如果为0则入栈
            if (--g.adjlist[p->adjvex].in==0)
            {
                stack[++top]=p->adjvex;
            }
            p=p->nextarc;
        }
    }
    if (count<g.vexnum)
        cout<<"图中存在环"<<endl;
    else
        cout<<"拓扑排序完成"<<endl;
}

int main(int argc, char* argv[])
{
    GraphTp g;
    CreateGraph(g);
    Top_Sort(g);
    return 0;
}
    

另外,书在首次将入度为0的顶点编号入栈的地方没有写"{",这样的结果是错误的,估计是排版的人弄错的.可以参考我的代码,填上相应的"{}"