From ecb091548b832afd3722b2c83b949396754feccc Mon Sep 17 00:00:00 2001
From: Alex Karle <alex@alexkarle.com>
Date: Sun, 4 Dec 2022 10:19:07 -0500
Subject: [PATCH] day4: Add solution

---
 2022/04/input   | 1000 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2022/04/sample  |    6 ++++++
 2022/04/sol.scm |   49 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1055 insertions(+)
 create mode 100644 2022/04/input
 create mode 100644 2022/04/sample
 create mode 100755 2022/04/sol.scm

diff --git a/2022/04/input b/2022/04/input
new file mode 100644
index 0000000..aa044e4
--- /dev/null
+++ b/2022/04/input
@@ -0,0 +1,1000 @@
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diff --git a/2022/04/sample b/2022/04/sample
new file mode 100644
index 0000000..9f9e9cf
--- /dev/null
+++ b/2022/04/sample
@@ -0,0 +1,6 @@
+2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8
diff --git a/2022/04/sol.scm b/2022/04/sol.scm
new file mode 100755
index 0000000..df23e85
--- /dev/null
+++ b/2022/04/sol.scm
@@ -0,0 +1,49 @@
+#!/usr/local/bin/chicken-csi -ss
+(import (chicken io)
+        (chicken string))
+
+;; part 1: find full overlaps between pairs
+;; that means just count where for a-b,x-y a<x and y<b (or vice versa)
+;; (no need to check x<b since implied by x<y)
+(define (overlaps? pair)
+  (let ((a (caar pair))
+        (b (cadar pair))
+        (x (caadr pair))
+        (y (cadadr pair)))
+    (or
+      (and (<= a x) (>= b y))
+      (and (<= x a) (>= y b)))))
+
+; part 2: no overlap: a > y or x > b
+(define (any-overlap? pair)
+  (let ((a (caar pair))
+        (b (cadar pair))
+        (x (caadr pair))
+        (y (cadadr pair)))
+    (not (or (> a y) (> x b)))))
+
+(define (parse-line l)
+  (let* ((ranges (string-split l ","))
+         (pair (map (lambda (r)
+                      (map (lambda (x) (string->number x))
+                           (string-split r "-")))
+                    ranges)))
+    pair))
+
+(define (filter pred lst)
+  (cond ((null? lst) '())
+        ((pred (car lst))
+         (cons (car lst) (filter pred (cdr lst))))
+        (else (filter pred (cdr lst)))))
+
+(define (part-1 pairs)
+  (length (filter overlaps? pairs)))
+
+(define (part-2 pairs)
+  (length (filter any-overlap? pairs)))
+
+(define (main args)
+  (let* ((lines (read-lines))
+         (pairs (map parse-line lines)))
+    (print (part-1 pairs))
+    (print (part-2 pairs))))
--
libgit2 1.8.1