the example graph: V=9, E=14
  Prim    total = 37
  Kruskal total = 37
  agree: yes

1000 random connected graphs (5..30 vertices, weights 1..20)
  disagreements between Prim and Kruskal: 0

shape     V         E           Prim ms     Kruskal ms  weights equal
sparse    200000    400000      104.9       26.3        yes
dense     2000      1000000     39.9        58.7        yes
