It is an overuse of maps and reduces, but let’s go through it step-by-step.

I start by slurping in the input day1.txt, which is a collection of newline delimited numbers representing multiple elves.
Then, I push that input through a series of transforms with the thread-last macro ->>.

Splitting the input by a double newline gives me each elf in it’s own sequence. The elves are delimited by blank lines (an additional newline character). Then I split each row by the newline character to give me every number in a row.

Next, I run Java’s Integer/parseInt to get the numerical values of each number in an elf row, then I coerce those values into
a vector using into.

After, I reduce the elf rows by summing each one, sort the rows in descending order, and take 3 elements from the front of the
sequence. My answer is then the first of the top 3 elf totals, and the sum of the top 3 elf totals.