From d195797bbc2a83c46056a9d3eef0ffaea231fca4 Mon Sep 17 00:00:00 2001
From: Jonathan Chan <jonathanhwchan@gmail.com>
Date: Thu, 8 Dec 2022 01:34:11 -0500
Subject: [PATCH] Day 8, absolutely disgusting

---
 input/08.txt |  99 +++++++++++++++++++++++++++++++++++++++++++
 src/08.rkt   | 116 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 215 insertions(+)
 create mode 100644 input/08.txt
 create mode 100644 src/08.rkt

diff --git a/input/08.txt b/input/08.txt
new file mode 100644
index 0000000..115d4da
--- /dev/null
+++ b/input/08.txt
@@ -0,0 +1,99 @@
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diff --git a/src/08.rkt b/src/08.rkt
new file mode 100644
index 0000000..b65f633
--- /dev/null
+++ b/src/08.rkt
@@ -0,0 +1,116 @@
+#lang racket
+
+(require "../lib.rkt")
+
+(define test
+  '("30373"
+    "25512"
+    "65332"
+    "33549"
+    "35390"))
+
+(define input
+  (~>> (problem-input 8) #;test
+       (map string->list)
+       (mmap char->number)))
+
+(define (get-tree r c)
+  (list-ref (list-ref input r) c))
+
+(define width (length (first input)))
+(define height (length input))
+
+(define (part1)
+  (define s1
+    (for/fold ([talls (set)])
+              ([r (range height)])
+      (for/fold ([talls talls]
+                 [tallest (get-tree r 0)]
+                 #:result talls)
+                ([c (range width)])
+        (define t (get-tree r c))
+        (if (< tallest t)
+            (values (set-add talls (cons r c)) t)
+            (values talls tallest)))))
+  (define s2
+    (for/fold ([talls s1])
+              ([r (range height)])
+      (for/fold ([talls talls]
+                 [tallest (get-tree r (sub1 width))]
+                 #:result talls)
+                ([c (reverse (range width))])
+        (define t (get-tree r c))
+        (if (< tallest t)
+            (values (set-add talls (cons r c)) t)
+            (values talls tallest)))))
+  (define s3
+    (for/fold ([talls s2])
+              ([c (range width)])
+      (for/fold ([talls talls]
+                 [tallest (get-tree 0 c)]
+                 #:result talls)
+                ([r (range height)])
+        (define t (get-tree r c))
+        (if (< tallest t)
+            (values (set-add talls (cons r c)) t)
+            (values talls tallest)))))
+  (define s4
+    (for/fold ([talls s3])
+              ([c (range width)])
+      (for/fold ([talls talls]
+                 [tallest (get-tree (sub1 height) c)]
+                 #:result talls)
+                ([r (reverse (range height))])
+        (define t (get-tree r c))
+        (if (< tallest t)
+            (values (set-add talls (cons r c)) t)
+            (values talls tallest)))))
+  (define s5
+    (for/fold ([talls s4])
+              ([r (range height)])
+      (~> talls
+          (set-add (cons r 0))
+          (set-add (cons r (sub1 width))))))
+  (define s6
+    (for/fold ([talls s5])
+              ([c (range width)])
+      (~> talls
+          (set-add (cons 0 c))
+          (set-add (cons (sub1 height) c)))))
+  (set-count s6))
+
+(define (score r c)
+  (define t (get-tree r c))
+  (define s1
+    (let loop ([c* (add1 c)])
+      (if (or (>= c* (sub1 width))
+              (>= (get-tree r c*) t))
+          (- c* c)
+          (loop (add1 c*)))))
+  (define s2
+    (let loop ([c* (sub1 c)])
+      (if (or (<= c* 0)
+              (>= (get-tree r c*) t))
+          (- c c*)
+          (loop (sub1 c*)))))
+  (define s3
+    (let loop ([r* (add1 r)])
+      (if (or (>= r* (sub1 height))
+              (>= (get-tree r* c) t))
+          (- r* r)
+          (loop (add1 r*)))))
+  (define s4
+    (let loop ([r* (sub1 r)])
+      (if (or (<= r* 0)
+              (>= (get-tree r* c) t))
+          (- r r*)
+          (loop (sub1 r*)))))
+  (* s1 s2 s3 s4))
+
+(define part2
+  (maximum
+   (for*/list ([r (range 1 (sub1 height))]
+               [c (range 1 (sub1 width))])
+     (score r c))))
+
+(show-solution (part1) part2)
\ No newline at end of file