From 6761c53d16fe52bca17b4a549f8d74c413c94992 Mon Sep 17 00:00:00 2001
From: Aryadev Chavali <aryadev@aryadevchavali.com>
Date: Mon, 26 Jun 2023 07:16:31 +0100
Subject: (1|2)+lisp files for puzzles 1 and 2

Includes code for both rounds, separated by comments.
---
 puzzle-1.lisp | 26 ++++++++++++++++++++++++++
 puzzle-2.lisp | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 puzzle-1.lisp
 create mode 100644 puzzle-2.lisp

diff --git a/puzzle-1.lisp b/puzzle-1.lisp
new file mode 100644
index 0000000..45d1921
--- /dev/null
+++ b/puzzle-1.lisp
@@ -0,0 +1,26 @@
+(defvar input (uiop:read-file-string "puzzle-1-input.txt"))
+(defvar *sep (format nil "~%~%"))
+
+(defun get-lists (input)
+  (let ((pos (search *sep input)))
+    (with-input-from-string (s (subseq input 0 pos))
+      (let ((converted
+              (loop
+                for line = (read-line s nil nil)
+                while line
+                collect (parse-integer line))))
+        (if (null pos)
+            (list converted)
+            (cons converted
+                  (get-lists (subseq input (+ pos 2)))))))))
+
+(defvar sums (sort (mapcar (lambda (lst) (reduce #'+ lst)) (get-lists input)) #'>))
+
+;; First challenge
+(format t "Top snacks: ~a" (car sums))
+
+;; Second challenge
+(let ((first (car sums))
+      (second (car (cdr sums)))
+      (third (car (cdr (cdr sums)))))
+  (format t "~a,~a,~a:>~a" first second third (+ first second third)))
diff --git a/puzzle-2.lisp b/puzzle-2.lisp
new file mode 100644
index 0000000..377b6ba
--- /dev/null
+++ b/puzzle-2.lisp
@@ -0,0 +1,54 @@
+(defvar input (uiop:read-file-string "puzzle-2-input.txt"))
+;; Each newline represents a new round, which we should parse on the go
+
+(defun sensible-convert-input (str)
+  (cond
+    ((or (string= str "X") (string= str "A")) 0)
+    ((or (string= str "Y") (string= str "B")) 1)
+    ((or (string= str "Z") (string= str "C")) 2)))
+
+;; Round 1
+(defvar rounds
+  (with-input-from-string (stream input)
+    (loop
+      for strategy = (read-line stream nil)
+      until (null strategy)
+      collect
+      (let ((opponent (subseq strategy 0 1))
+            (yours (subseq strategy 2 3)))
+        (list (sensible-convert-input opponent) (sensible-convert-input yours))))))
+
+(loop
+  for round in rounds
+  until (null round)
+  sum
+  (destructuring-bind (opp you) round
+    (+
+     1 you ;; base score
+     (cond  ; outcome score
+       ((eq you opp) 3)
+       ((eq (mod (+ 1 opp) 3) you) 6)
+       (t 0)))))
+
+;; Round 2.
+
+;; We can still use the same rounds data as previously, just
+;; reinterpret it in when doing the sum.
+
+(defun get-correct-choice (opponent outcome)
+  (case outcome
+    (0 (mod (- opponent 1) 3))
+    (1 opp)
+    (2 (mod (+ 1 opponent) 3))
+    (t 0)))
+
+(loop for round in rounds
+      sum
+      (destructuring-bind (opp you) round
+        (let ((choice (get-correct-choice opp you)))
+          (+ 1 choice
+             (case you ;; outcome -> score
+               (0 0)
+               (1 3)
+               (2 6)
+               (t 0))))))
-- 
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