=== Ex 12.1  greedy change-making with the coins {1, 4, 6} ===
  amount  8: greedy uses 3 coins, the optimum uses 2
  amount  9: greedy uses 4 coins, the optimum uses 3
  amount 14: greedy uses 4 coins, the optimum uses 3
  amount 15: greedy uses 5 coins, the optimum uses 4
  amounts 1..30 on which greed loses: 8

=== Ex 12.3  BFS from C instead of A ===
  source A   d: A=0 B=1 C=1 D=2 E=2 F=2 G=3 H=3 I=4 
            pi: A<-- B<-A C<-A D<-B E<-B F<-C G<-D H<-E I<-G 
  source C   d: A=1 B=2 C=0 D=3 E=1 F=1 G=2 H=2 I=3 
            pi: A<-C B<-A C<-- D<-B E<-C F<-C G<-E H<-E I<-G 
  the eccentricity of A is 4 and of C is 3, so the two trees differ in shape

=== Ex 12.5  the same digraph, two outer-loop orders ===
  outer loop A,B,C,D,E,F,G
    d/f: A=1/12 B=2/5 C=6/11 D=3/4 E=7/10 F=8/9 G=13/14 
    tree 5, back 2, forward 1, cross 3
    A->B:T A->C:T A->D:F B->D:T C->D:C C->E:T D->A:B E->F:T F->E:B G->C:C G->F:C 
  outer loop G,F,E,D,C,B,A
    d/f: A=4/7 B=5/6 C=2/13 D=3/8 E=9/12 F=10/11 G=1/14 
    tree 6, back 4, forward 1, cross 0
    A->B:T A->C:B A->D:B B->D:B C->D:T C->E:T D->A:T E->F:T F->E:B G->C:T G->F:F 
  the COUNT of back edges changed (2 then 4) but neither is zero:
  the verdict 'not acyclic' is order-independent, the classification is not

=== Ex 12.7  an instance where 'shortest duration first' fails ===
  a1=[0,5), a2=[4,6), a3=[5,10)
  shortest duration picks a2 (2 units) and then nothing: a2  -> size 1
  earliest finish picks: a1 a3  -> size 2

=== Ex 12.9  transforming the weights ===
  original       weight    31   tree BC DE AB FG CD EF GH 
  every w + 10   weight   101   tree BC DE AB FG CD EF GH  (same tree)
                 check: 31 + 7*10 = 101
  every w square weight   209   tree BC DE AB FG CD EF GH  (same tree)
  every 20 - w   weight    79   tree FH GH EG CE DF BD AC  (DIFFERENT)

=== Ex 12.11  union by rank, measured ===
  no rank, no compression:  total parent hops for 100000 finds = 4999950000
  union by rank + compression: total parent hops = 99999
