#include"stdio.h"
#include"conio.h"
#include"ctype.h"
#include"alloc.h"
#define TRUE 1
#define FALSE 0
#define FOUND 1
#define MAXSIZE 20
typedef struct su_node
{
 int succ_no;
 struct su_node *next;
}node1;
typedef struct s_node
{
 int pred_count;
 int tag;
 struct su_node *succ_node_ptr;
}node2;
node2 graph[MAXSIZE+1];
int cycles=0,cr=0;
void init_graph()
{
  int i;
  for(i=1;i<=MAXSIZE;i++)
  {
   graph[i].succ_node_ptr=NULL;
   graph[i].pred_count=0;
   graph[i].tag=FALSE;
  }
}
void install(int pd,int su)
{
 node1 **pp,*p=NULL;
 graph[pd].pred_count+=1;
 p=(node1 *)malloc(sizeof(node1));
 p->succ_no=su;
 p->next=NULL;
 pp=&(graph[pd].succ_node_ptr);
 while(*pp!=NULL)
 pp=&((*pp)->next);
 *pp=p;
}
void create()
{
 int edge,pred,succ,i;
 printf("\n ENTER THE NUMBER OF EDGES");
 scanf("%d",&edge);
 for(i=1;i<=edge;i++)
 {
  printf("\n ENTER THE PREDECESSOR");
  scanf("%d",&pred);
  printf("\n ENTER THE SUCESSOR");
  scanf("%d",&succ);
  install(pred,succ);
 }
}

 void print_graph(int n)
 {
 int i;
 node1 *p;
 for(i=1;i<=n;i++)
 {
 printf("\n %d NO. OF PREDECCESORS OF %d",graph[i].pred_count,i);
  p=graph[i].succ_node_ptr;
  printf("\n cycle from %d\n",i);
  while(p!=NULL)
  {
   printf("\t\t%d-->%d\n",i,p->succ_no);
   p=p->next;
  }
 }
}
void drs(int st,int ct)
{
 node1 *p;
 int ct_node;
 printf("\t%d-->",cr);
 if(graph[ct].tag==TRUE)
 {
  if(st==ct)
  {
   cr=FOUND;
   cycles++;
   getch();
   clrscr();
   return;
  }
 }
 graph[ct].tag=TRUE;
 p=graph[ct].succ_node_ptr;
while(p!=NULL)
{
ct_node=p->succ_no;
drs(st,ct_node);
p=p->next;
}
clrscr();
graph[ct].tag=FALSE;
}
void cycle(int n)
{
 int i;
 for(i=1;i<=n;i++)
 {
  drs(i,i);
  }
  if(cycles>0)
  {
   printf("CYCLES ARE FOUND");
   printf("THE NUMBER OF CYCLES :%d\n",cycles);
  }
 }
 void main()
 {
  int n;
  clrscr();
  printf("ENTER THE NUMBER OF NODES");
  scanf("%d",&n);
  init_graph();
  create();
  cycle(n);
  print_graph(n);
  getch();
 }