C Program on Topological Sort

   #include<stdio.h>
   #define MAX 200
   int n,adj[MAX][MAX];
   int front = -1,rear = -1,queue[MAX];
   void main()
   {
     int i,j = 0,k;
     int topsort[MAX],indeg[MAX];
     create_graph();
     printf(“The adjacency matrix is:\n”);
     display();
     for(i=1;i<+n;i++)
     {
     indeg[i]=indegree(i);
       if(indeg[i]==0)
         insert_queue(i);
     }
     while(front<=rear)
     {
       k=delete_queue();
       topsort[j++]=k;
       for(i=1;ilt;=n;i++)
       {
         if(adj[k][i]==1)
         {
           adj[k][i]=0;
           indeg[i]=indeg[i]-1;
           if(indeg[i]==0)
             insert_queue(i);
         }
       }
     }
     printf("Nodes after topological sorting are:\n");
     for(i=0;i<=n;i++)
     printf("%d",topsort[i]);
     printf("\n");
   }
   create_graph()
   {
     int i,max_edges,origin,destin;
     printf("\n Enter number of vertices:");
     scamf("%d",&n);
     max_edges = n * (n - 1);
     for(i = 1;i <= max_edges;i++)
     {
       printf("\n Enter edge %d (00 to quit):",i);
       scanf("%d %d",&origin,&destin);
       if((origin == 0) && (destin == 0))
       {
         printf("Invalid edge!!\n");
         i–;
       }
       else
         adj[origin][destin] = 1;
     }
     return;
   }
   display()
   {
     int i,j;
     for(i = 0;i <= n;i++)
     {
       for(j = 1;jrear)
       {
         printf(“Queue Underflow”);
         return;
       }
       else
       {
         del_item = queue[front];
         front = front + 1;
         return del_item;
       }
     }
     int indegree(int node)
     {
       int i,in_deg = 0;
       for(i = 1;i <= n;i++)
       if(adj[i][node] == 1)
         in_deg++;
       return in_deg;
     }
   }