=== Exercise 4: second largest, in O(h) ===
  50(0){30(0){20(0),40(0)},70(0){60(0),80(0)}}
  largest = 80, second largest = 70
  50(1){30(0),70(-1){65(0),.}}
  largest = 70, second largest = 65
  50(-1){30(0),.}
  largest = 50, second largest = 30

=== Exercise 8: why the case test needs <= and not < ===
  start          : 50(-1){20(0){10(0){5(0),15(0)},30(1){.,40(0)}},70(-1){60(0),.}}   AVL=yes
  delete 60, <=0 : 20(1){10(0){5(0),15(0)},50(-1){30(1){.,40(0)},70(0)}}   AVL=yes
  delete 60, <0  : 30(-1){20(-2){10(0){5(0),15(0)},.},50(0){40(0),70(0)}}   AVL=NO

=== Exercise 7: one deletion, many rebalancings ===
  h   N(h)   deleting the largest key: rotations
   2      4                           1   (still AVL: yes, height 2 -> 1)
   3      7                           1   (still AVL: yes, height 3 -> 2)
   4     12                           2   (still AVL: yes, height 4 -> 3)
   5     20                           2   (still AVL: yes, height 5 -> 4)
   6     33                           3   (still AVL: yes, height 6 -> 5)
   7     54                           3   (still AVL: yes, height 7 -> 6)
   8     88                           4   (still AVL: yes, height 8 -> 7)
   9    143                           4   (still AVL: yes, height 9 -> 8)
  10    232                           5   (still AVL: yes, height 10 -> 9)
  11    376                           5   (still AVL: yes, height 11 -> 10)
  12    609                           6   (still AVL: yes, height 12 -> 11)

=== Exercise 5: node inspections on a perfect tree ===
     n      slow    (n+1)lg(n+1)-n     fast
     7        17                17        7   match
    15        49                49       15   match
    31       129               129       31   match
    63       321               321       63   match
   127       769               769      127   match
   255      1793              1793      255   match
   511      4097              4097      511   match
  1023      9217              9217     1023   match
  2047     20481             20481     2047   match
