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author | Aryadev Chavali <aryadev@aryadevchavali.com> | 2023-06-26 08:33:59 +0100 |
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committer | Aryadev Chavali <aryadev@aryadevchavali.com> | 2023-06-26 08:33:59 +0100 |
commit | 29cacf2394a6d64f1ab3d5ba13a35f3beb08c3c7 (patch) | |
tree | 36b2ff2c409b9956e83481589fba9f38326eae08 /puzzle-4.lisp | |
parent | f8a0d0f1acc50711e470999434f7f8f504188b2e (diff) | |
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(3|4)+lisp files for puzzles 3 and 4
Diffstat (limited to 'puzzle-4.lisp')
-rw-r--r-- | puzzle-4.lisp | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/puzzle-4.lisp b/puzzle-4.lisp new file mode 100644 index 0000000..be842d3 --- /dev/null +++ b/puzzle-4.lisp @@ -0,0 +1,59 @@ +;; Example input: a-b,c-d which denotes [a,b] and [c,d] + +;; We want to find if [c,d] < [a,b] or vice versa (complete inclusion) +;; and since we're working with integers, it's simply checking if the +;; bounds are included i.e. c in [a,b] and d in [a,b] + +(defvar input (uiop:read-file-string "puzzle-4-input.txt")) + +(defun parse-bound (str) + "Given STR=\"a-b\" return (a b)" + (let* ((sep (search "-" str)) + (first (subseq str 0 sep)) + (second (subseq str (+ sep 1)))) + (list (parse-integer first) (parse-integer second)))) + +(defvar completed-parse + (with-input-from-string (s input) + (loop for line = (read-line s nil) + until (null line) + collect + ;; given a-b,c-d we want ((a b) (c d)) + (let* ((sep (search "," line)) + (first-bound (subseq line 0 sep)) + (second-bound (subseq line (+ sep 1)))) + (list (parse-bound first-bound) (parse-bound second-bound)))))) + +(defun complete-inclusion (first-bound second-bound) + (destructuring-bind (a b) first-bound + (destructuring-bind (c d) second-bound + (or + (and + (>= a c) (<= a d) + (>= b c) (<= b d)) + (and + (>= c a) (<= c b) + (>= d a) (<= d b)))))) + +(defvar round-1-answer (length (remove-if #'null + (mapcar (lambda (pair) + (destructuring-bind (first second) pair + (complete-inclusion first second))) + completed-parse)))) + +;; Round 2: any overlap at all. Basically just overhaul the inclusion +;; function and then do the same answer checking. +(defun any-inclusion (first second) + (destructuring-bind (a b) first + (destructuring-bind (c d) second + ;; How about doing this through negation? [a,b] does not overlap with [c,d] at all if either b < c or a > d. + (not + (or + (< b c) + (> a d)))))) + +(defvar round-2-answer (length (remove-if #'null + (mapcar (lambda (pair) + (destructuring-bind (first second) pair + (any-inclusion first second))) + completed-parse)))) |