- find all the 'word logs'

- - necessarily an O(n^2) algorithm, assuming we can check a

- string of digits in constant time

+ - looking up a single sequence of digits in the wordTree

+ is O(1), since the wordTree has a fixed depth defined by

+ - here we use an O(n^2) algorithm to find sub-sequences

+ of the original digits, so it is O(n^2) overall.

+ - we could use an algorithm that looks up a sequence of

+ digits *and* all the prefixes of that sequence in a

+ single pass through the wordTree, which would allow

+ us to find all the words in the digit sequence in O(n)

+ time. But it isn't the limiting factor.

- add in all necessary 'digit logs'

- depends on the number and spacing of word logs

- find all routes across the river