V = 9, E = 14, root = a

step  1: extract a  key=0
        Q = {b:4/a, h:8/a, c:INF, d:INF, e:INF, f:INF, g:INF, i:INF}
step  2: extract b  key=4  add edge (a,b) w=4  running total=4
        Q = {c:8/b, h:8/a, d:INF, e:INF, f:INF, g:INF, i:INF}
step  3: extract c  key=8  add edge (b,c) w=8  running total=12
        Q = {i:2/c, f:4/c, d:7/c, h:8/a, e:INF, g:INF}
step  4: extract i  key=2  add edge (c,i) w=2  running total=14
        Q = {f:4/c, g:6/i, d:7/c, h:7/i, e:INF}
step  5: extract f  key=4  add edge (c,f) w=4  running total=18
        Q = {g:2/f, d:7/c, h:7/i, e:10/f}
step  6: extract g  key=2  add edge (f,g) w=2  running total=20
        Q = {h:1/g, d:7/c, e:10/f}
step  7: extract h  key=1  add edge (g,h) w=1  running total=21
        Q = {d:7/c, e:10/f}
step  8: extract d  key=7  add edge (c,d) w=7  running total=28
        Q = {e:9/d}
step  9: extract e  key=9  add edge (d,e) w=9  running total=37
        Q = {}

MST edges, in the order Prim added them:
  (a,b) w=4
  (b,c) w=8
  (c,i) w=2
  (c,f) w=4
  (f,g) w=2
  (g,h) w=1
  (c,d) w=7
  (d,e) w=9
  edge count = 8  (|V|-1 = 8)
  total weight = 37   (accumulated during the run: 37)
