Breadth First Search (BFS)

Breadth First Search algorithm pseudocode:

//color[]= {white=not visited, gray=visiting-not finished, black=visited}
//prev[]= parent
//d[]= distance

BFS(G) 
{
 //initialization
 for each vertex u in V-{s}
 {
  color[u]=WHITE;
  prev[u]=NIL;
  d[u]=inf;
 }
        //initializing source
 color[s]=GRAY;
 d[s]=0; 
 prev[s]=NIL;
 Q=empty;
 ENQUEUE(Q,s);
 
 While(Q not empty)
 {
  u = DEQUEUE(Q);
  for each v in adj[u]{
  if (color[v] == WHITE)
  {
   color[v] = GREY;
   d[v] = d[u] + 1;
   prev[v] = u;
   Enqueue(Q, v);
  }
 }
 color[u] = BLACK;
 }
}

Path print:

Print-Path(G, s, v)

if v = s
        then print s
        else   if π[v] ← NIL
                then  print "no path exists from " s "to" v"
                else   Print-Path(G, s, π[v])
                        print v