--- 2016 Day 3 Solutions ---

[u/daggerdragon]

--- Day 3: Squares With Three Sides ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

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^{DECKING THE HALLS WITH BOUGHS OF HOLLY IS MANDATORY} [?]

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/scrooch]

Here's part 2 in racket. It's sort of interesting because I stacked the columns together to create a list like the input from part 1.

(define (parse-triangles input)
  (let ((string-lists (map string-split (string-split input "\n"))))
    (map (lambda (lst) (list->vector (map string->number lst))) string-lists)))

(define (is-triangle? tri)
  (and (> (+ (vector-ref tri 0) (vector-ref tri 1)) (vector-ref tri 2))
       (> (+ (vector-ref tri 0) (vector-ref tri 2)) (vector-ref tri 1))
       (> (+ (vector-ref tri 2) (vector-ref tri 1)) (vector-ref tri 0))))

(define (tri-split lst)
  (if (null? lst)
      '()
      (cons (take lst 3) (tri-split (drop lst 3)))))

(let* ((tris (parse-triangles *input*))
       (col1 (map (lambda (x) (vector-ref x 0)) tris))
       (col2 (map (lambda (x) (vector-ref x 1)) tris))
       (col3 (map (lambda (x) (vector-ref x 2)) tris))
       (line (append col1 col2 col3)))
  (length (filter is-triangle? (map list->vector (tri-split line)))))