拓扑排序

（1）在有向图中选一个没有前驱的顶点且输出之

（2）从图中删除该顶点和所有以它为尾的弧

#include “stdafx.h”
#include “malloc.h”

#define MAX_VERTEX_NUM 20
#define STACK_INIT_SIZE 100
#define STACKINCREMENT 10
#define ERROR 0
#define OK 1
#define OVERFLOW -1
typedef int InfoType;
typedef char VertexType;
typedef int Status;
int indegree[60];
//图的定义
typedef struct ArcNode{
 int adjvex;
 struct ArcNode *nextarc;
 InfoType *info;
}ArcNode;
typedef struct VNode{
 VertexType data;
 ArcNode *firstarc;
}VNode,AdjList[MAX_VERTEX_NUM];
typedef struct{
 AdjList vertices;
 int vexnum,arcnum;
 int kind;
}ALGraph;
//定义一下栈
typedef int SElemType;
typedef struct{
 SElemType *base;
 SElemType *top;
 int stacksize;
}SqStack;
//初始化栈
Status InitStack(SqStack &S){
 S.base=(SElemType*)malloc(STACK_INIT_SIZE * sizeof(SElemType));
 if(!S.base) return (OVERFLOW);
 S.top=S.base;
 S.stacksize=STACK_INIT_SIZE;
 return OK;
}
//入栈
Status Push(SqStack &S,SElemType e){
 if(S.top-S.base>=S.stacksize){
  S.base=(SElemType *)realloc(S.base,(S.stacksize+STACKINCREMENT)*sizeof(SElemType));
  if(!S.base) return (OVERFLOW);
  S.top=S.base+S.stacksize;
  S.stacksize+=STACKINCREMENT;
 }
 *S.top++=e;
 return OK;
}
//出栈
Status Pop(SqStack &S,SElemType &e){
 if(S.top==S.base) return ERROR;
 e=*–S.top;
 return OK;
}
//判断栈是否为空
Status StackEmpty(SqStack S){
 if(S.top==S.base)
  return OK;
 else
  return ERROR;
}

int LocateVex(ALGraph G, VertexType v) {
 int i ;
 for(i=0;i<G.vexnum;++i){
  if(v==G.vertices[i].data)
   return i;
 }
 return OVERFLOW;
}

//创建一个有向图
Status CreateDG(ALGraph &G) { VertexType v1, v2; int i,k,j; ArcNode *p,*q;
printf(“请输入节点个数\n”);
scanf(“%d”, &G.vexnum);
printf(“请输入边个数\n”);
scanf(“%d”, &G.arcnum);
printf(“请输入节点元素\n”);
getchar();
for (i = 0; i < G.vexnum; ++i){
 scanf(“%c”, &G.vertices[i].data);
 getchar();
}
for (i = 0; i < G.vexnum; ++i)
 G.vertices[i].firstarc = NULL;
for (k = 0; k < G.arcnum; ++k) {
 printf(“请输入边\n”);
 scanf(“%c”,%c, &v1,&v2);
  getchar();
 i = LocateVex(G, v1);
 j = LocateVex(G, v2);
 p = (ArcNode *)malloc(sizeof(ArcNode));
 if (!G.vertices[i].firstarc)
  G.vertices[i].firstarc = p;
 else {
  for (q = G.vertices[i].firstarc;q->nextarc;q = q->nextarc);
  q->nextarc = p;
 }
 p->adjvex = j;
 p->nextarc = NULL;
}
return OK;
}

Status FindInDegree(ALGraph G){
 int k;
 for(int i=0;i<G.vexnum;i++){
  indegree[i]=0;
 }
 for(int i=0;i<G.vexnum;i++){

  ArcNode *p=G.vertices[i].firstarc;
  while(p)
  {
   indegree[p->adjvex]++;
   p=p->nextarc;
  }
 }
 return OK;
}

//拓扑排序
Status TopologicalSort(ALGraph G){
 int i,k;
 ArcNode *p;
 SqStack S;
 CreateDG(G);
 FindInDegree(G);
 InitStack(S);
 for(i=0;i<G.vexnum;i++){
  if(!indegree[i]) {
   Push(S,i);
  }
 }
 int count=0;

printf(“拓扑排序结果是：”);
 while(!StackEmpty(S)){
  Pop(S,i);
  printf(“%c “,G.vertices[i].data);
  count++;
  for(p=G.vertices[i].firstarc;p;p=p->nextarc){
   k=p->adjvex;
   if(!(–indegree[k])) Push(S,k);
  }
 }
 if(count<G.vexnum) return ERROR;
 else return OK;
}
void main(){
 ALGraph G;
 TopologicalSort(G);

}