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#lang racket
(require advent-of-code
fancy-app
threading
(only-in relation ->number))
(define command-output (~> (fetch-aoc-input (find-session) 2022 7) (string-split "\n")))
(define (parse-commands cmds)
(define (update-sizes h path size)
(match path
['() h]
[(list* _ fs) (update-sizes (hash-update h path (+ _ size) 0) fs size)]))
(for/fold ([folders (hash)] [current-path '()] [previously-seen? #false] #:result folders)
([cmd (in-list cmds)])
(match cmd
["$ ls" (values folders current-path (hash-has-key? folders current-path))]
["$ cd /" (values folders '("/") #false)]
["$ cd .." (values folders (rest current-path) #false)]
[(regexp #px"\\$ cd (.+)" (list _ folder)) (values folders (cons folder current-path) #false)]
[(regexp #px"dir (.+)") (values folders current-path previously-seen?)]
[(regexp #px"(.+) (.+)" (list _ (app ->number size) _))
(cond
[previously-seen? (values folders current-path previously-seen?)]
[else (values (update-sizes folders current-path size) current-path previously-seen?)])])))
(define folders (parse-commands command-output))
;; part 1
(for/sum ([(_ v) (in-hash folders)] #:when (<= v 100000)) v)
;; part 2
(define required-to-delete (- 30000000 (- 70000000 (hash-ref folders '("/")))))
(~>> folders hash-values (filter (> _ required-to-delete)) (apply min))
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