--- building the eight-node tree of Chapter 6 with insertHB ---
  built       13(-1){10(-1){5(0){4(0),6(0)},11(0)},15(1){.,16(0)}}   [h=3, rot=0, AVL=yes]
--- insert 14, no rotation expected ---
  insert 14   13(-1){10(-1){5(0){4(0),6(0)},11(0)},15(0){14(0),16(0)}}   [h=3, rot=0, AVL=yes]
--- insert 3, Left-Left expected ---
  insert 3    13(-1){5(0){4(-1){3(0),.},10(0){6(0),11(0)}},15(1){.,16(0)}}   [h=3, rot=1, AVL=yes]
--- insert 7, Left-Right expected ---
  insert 7    13(-1){6(0){5(-1){4(0),.},10(0){7(0),11(0)}},15(1){.,16(0)}}   [h=3, rot=2, AVL=yes]
--- root 30, left 5, right 35{32,40}; insert 45, Right-Right ---
  built       30(1){5(0),35(0){32(0),40(0)}}   [h=2, rot=0, AVL=yes]
  insert 45   35(0){30(0){5(0),32(0)},40(1){.,45(0)}}   [h=2, rot=1, AVL=yes]
--- insert 15 into 5{2{1,4{3,.}},7{6,9{.,16}}}, Right-Left ---
  built       5(0){2(1){1(0),4(-1){3(0),.}},7(1){6(0),9(1){.,16(0)}}}   [h=3, rot=0, AVL=yes]
  insert 15   5(0){2(1){1(0),4(-1){3(0),.}},7(1){6(0),15(0){9(0),16(0)}}}   [h=3, rot=2, AVL=yes]
--- the deletion example of Chapter 6 ---
  built       44(1){17(1){.,32(0)},62(0){50(0){48(0),54(0)},78(1){.,88(0)}}}   [h=3, rot=0, AVL=yes]
  delete 32   62(-1){44(1){17(0),50(0){48(0),54(0)}},78(1){.,88(0)}}   [h=3, rot=1, AVL=yes]
  delete 62   44(1){17(1){.,32(0)},54(0){50(-1){48(0),.},78(1){.,88(0)}}}   [h=3, rot=0, AVL=yes]
  delete 99   44(1){17(1){.,32(0)},62(0){50(0){48(0),54(0)},78(1){.,88(0)}}}   [h=3, rot=0, AVL=yes]
--- stress test: insert 1..1000 in order, then delete them all ---
  n = 1000, height = 9, AVL = yes, rotations = 990
  theoretical bound 1.4405*lg(n+2)-1.3277 = 13.032  ->  height <= 13: satisfied
  after deleting all: nodes = 0, isEmpty = true, rotations = 491
