Day 4 Part 2

diff --git a/src/day04.fnl b/src/day04.fnl
index 5d422141d3fe483ba6a444a104fbf9d6cac7eb93..2488a1e462f4fe99fef845ad77dc075b825951bb 100644 (file)
--- a/src/day04.fnl
+++ b/src/day04.fnl
@@ -13,20 +13,31 @@
     (or (and (>= r2l r1l) (<= r2h r1h))
         (and (>= r1l r2l) (<= r1h r2h)))))
 
+(defn range-overlaps [r1 r2]
+  (let [[r1l r1h] r1
+        [r2l r2h] r2]
+    (or (and (>= r1h r2l) (<= r1l r2h))
+        (and (>= r2h r1l) (<= r2l r1h)))))
+
 (comment
   (parse-range "2-4")
   (parse-pair "2-4,6-8")
   (range-contains (unpack (parse-pair "2-8,3-7")))
   (range-contains (unpack (parse-pair "5-7,7-9")))
   (range-contains (unpack (parse-pair "6-6,4-6")))
+  (range-overlaps (unpack (parse-pair "2-4,6-8")))
   (part1 ["2-4,6-8"
           "2-3,4-5"
           "5-7,7-9"
           "2-8,3-7"
           "6-6,4-6"
           "2-6,4-8"])
-  )
-
+  (part2 ["2-4,6-8"
+          "2-3,4-5"
+          "5-7,7-9"
+          "2-8,3-7"
+          "6-6,4-6"
+          "2-6,4-8"]))
 
 (defn part1 [lines]
   (->> lines 
@@ -35,7 +46,10 @@
        (#)))
 
 (defn part2 [lines]
-  )
+  (->> lines 
+       (c.map parse-pair)
+       (c.filter #(range-overlaps (unpack $1)))
+       (#)))
 
 (comment
   (part1 (c.lines "input/day04.txt"))