G = [ [0,0,1,0,1,1,0], [0,0,1,1,0,1,0], [1,1,0,1,1,1,0], [0,1,1,0,0,0,0],
      [1,0,1,0,0,0,1], [1,1,1,0,0,0,0], [0,0,0,0,1,0,0] ]

visited = [ 0 for i in range(len(G)) ]

def find_cycle(G, current, parent):
    visited[current] = 1
    print(current, end=" ")
    for i in range(len(G)):
         if G[current][i] == 1 and visited[i] == 0:
              find_cycle(G, i, current)
         elif G[current][i] == 1 and visited[i] == 1 and i != parent:
              print("Kreis gefunden.")
              return

find_cycle(G, 0, 0)