Hu Chunming / sip_server

  distances from start vertex:
  distance(0) = 0
  distance(1) = 6
  distance(2) = 1
  distance(3) = 4
  distance(4) = 5
  
  shortest paths tree
  0 --> 2
  1 -->
  2 --> 3
  3 --> 4
  4 --> 1