Simple topological sort pseudocode

void topsort( graph G )

{

QUEUE Q;

unsigned int counter;

vertex v, w;

/*1*/        Q = create_queue( NUM_VERTEX ); make_null( Q ); counter =  0;

/*2*/        for each vertex v

/*3*/             if( indegree[v] =   0 )

/*4*/                  enqueue( v, Q );

/*5*/        while( !is_empty( Q ) )

{

/*6*/             v = dequeue( Q );

/*7*/             top_num[v] = ++counter; /* assign next number */

/*8*/             for each w adjacent to v

/*9*/                  if( --indegree[w] =  0 )

/*10*/                      enqueue( w, Q );

}

/*11*/       if( counter != NUM_VERTEX )

/*12*/            error("Graph has a cycle");

/*13*/       dispose_queue( Q ); /* free the memory */

}