#12 wrong. #17–19 ran out of time but solved afterward. #21 took too much time but was solvable.
#22–25 not attempted. The others all right. Good try. :) :) :)
Main focus: improve pacing and find more efficient approaches.
Reviewed #3, #6, #8, #12, #14, #16, #19, and #21.
She can solve these problems; our focus was on whether there are cleaner,
faster, and more efficient approaches.
