def BFS(G):
     queue = []
     visited = [ 0 for i in range(len(G)) ]
     queue.append(0)
     visited[0] = 1
     while len(queue) > 0:
          current = queue.pop(0)
          print(current, end=" ")
          for j in G[current]:
               if visited[j] == 0:
                    visited[j] = 1
                    queue.append(j)

BFS([ [2,4,5], [2,3,5], [0,1,3,4,5], [1,2], [0,2,6], [0,1,2], [4] ])