=== Dijkstra on the Chapter 13 graph (s,u,v,x,y) ===
    initialize :  s=  0  u=inf  v=inf  x=inf  y=inf
     extract s :  s=  0  u= 10  v=inf  x=  5  y=inf
     extract x :  s=  0  u=  8  v= 14  x=  5  y=  7
     extract y :  s=  0  u=  8  v= 13  x=  5  y=  7
     extract u :  s=  0  u=  8  v=  9  x=  5  y=  7
     extract v :  s=  0  u=  8  v=  9  x=  5  y=  7

=== Bellman-Ford on the Chapter 13 graph (s,t,x,y,z) ===
    initialize :  s=  0  t=inf  x=inf  y=inf  z=inf
        pass 1 :  s=  0  t=  6  x=  4  y=  7  z=  2
        pass 2 :  s=  0  t=  2  x=  4  y=  7  z=  2
        pass 3 :  s=  0  t=  2  x=  4  y=  7  z= -2
        pass 4 :  s=  0  t=  2  x=  4  y=  7  z= -2
returns true (no negative cycle)
