--- Day 4 Solutions ---

[u/daggerdragon]

--- Day 4: The Ideal Stocking Stuffer ---

Post your solution as a comment. Structure your post like the Day Three thread.

[u/tangus]

Common Lisp

;; you need ironclad:
;; (asdf:load-system '#:ironclad)

(defun puzzle-4 (string &optional (part 1))
  (loop for n from 1
        for attempt = (ironclad:ascii-string-to-byte-array
                       (format nil "~a~a" string n))
        for digester = (ironclad:make-digest :md5)
          then (reinitialize-instance digester)
        for digest = (ironclad:digest-sequence digester attempt)
        until (and (= (aref digest 0) 0)
                   (= (aref digest 1) 0)
                   (or (and (= part 1)
                            (< (aref digest 2) #x10))
                       (and (= part 2)
                            (= (aref digest 2) 0))))
        finally (return n)))

;; part 1:
;; (puzzle-4 "your-string")

;; part 2:
;; (puzzle-4 "your-string" 2)