我试图找出有向图中是否存在循环。 它的方法是什么? 算法也有帮助..
我使用邻接列表实现了图形,到目前为止一切正常
代码
#include<stdio.h>
#include<stdlib.h>
typedef struct Graph
{
int vertex;
struct Graph *next;
}Graph;
Graph *g[10];
void initializeGraph(int n)
{
int i;
for(i=0;i<n;i++)
{
g[i]=(Graph*)malloc(sizeof(Graph));
g[i]->vertex=i;
g[i]->next=NULL;
}
}
void addEdge(int v,int u)
{
Graph *head=g[v];
while(head->next)
head=head->next;
head->next=(Graph*)malloc(sizeof(Graph));
head=head->next;
head->next=NULL;
head->vertex=u;
}
void printGraph(int n)
{
Graph *head;
int i;
for(i=0;i<n;i++)
{
head=g[i];
printf("\n");
while(head)
{
if(head->next)
printf("%d ---> ",head->vertex);
else
printf("%d ",head->vertex);
head=head->next;
}
}
}
void checkCycle(int v,int n)
{
}
int main()
{
int n,e,i,a[100],v,u;
printf("\nEnter the number of vertices - ");
scanf("%d",&n);
initializeGraph(n);
printf("\nEnter the number of edges - ");
scanf("%d",&e);
printf("\nVertices are - ");
for(i=0;i<n;i++)
printf("%d ",i);
printf("\nEnter the edges separated by space - ");
for(i=0;i<e;i++)
{
scanf("%d%d",&v,&u);
addEdge(v,u);
}
printGraph(n);
checkCycle(0,n);
printf("\n\n");
}
如果任何人都可以完成这项功能,那真的很有帮助! 感谢
** EDIT1:** 我试过这个
//Global arrays - visited[],isCycle[]
//visited[] is initialized to 0
//isCycle[] initialized to -1
//Method call : checkCycle(0,n);
int checkCycle(int v,int n)
{
Graph *head;
int w;
visited[v]=1;
head=g[v]->next;
while(head)
{
w=head->vertex;
if(visited[w])
return 1;
if(isCycle[w]==-1)
checkCycle(w,n); //We haven't visited that vertex yet
else
return 0; //We visited this vertex before but a cycle was not found
head=head->next;
}
visited[v]=0;
isCycle[v]=0;
return 0;
}
**Sample Input 1** -
Enter the number of vertices - 4
Enter the number of edges - 4
Vertices are - 0 1 2 3
Enter the edges separated by space - 0 1
1 2
2 3
3 0
0 ---> 1
1 ---> 2
2 ---> 3
3 ---> 0
Cycle Does not exist
**Sample Input 2**-
Enter the number of vertices - 4
Enter the number of edges - 3
Vertices are - 0 1 2 3
Enter the edges separated by space - 0 1
1 2
2 3
0 ---> 1
1 ---> 2
2 ---> 3
3
Cycle Does not exist
注意:在每个案例输出中 - 周期不存在。
答案 0 :(得分:1)
:你总是得到&#34;周期不存在&#34;因为你发现它时没有回复正确的答案。
程序中唯一的错误是
的状态检查if(isCycle[w] == -1)
return checkCycle(w, n);
在此之前你没有返回正确的答案,所以默认你发送了错误的答案,即返回false。 :)
快乐编码!!!