commit 0dfc884264f32af054892d3c606cb26e682c633e
parent 6513fd0b73342766cf82f9ad98942928cee08fbc
Author: Martin Ashby <martin@ashbysoft.com>
Date: Thu, 11 Dec 2025 20:52:15 +0000
Day 2 part 1
Diffstat:
3 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/02.input b/02.input
@@ -0,0 +1 @@
+61-71,12004923-12218173,907895-1086340,61083-74975,7676687127-7676868552,3328-4003,48-59,3826934-3859467,178-235,75491066-75643554,92-115,1487-1860,483139-586979,553489051-553589200,645895-722188,47720238-47818286,152157-192571,9797877401-9798014942,9326-11828,879837-904029,4347588-4499393,17-30,1-16,109218-145341,45794-60133,491-643,2155-2882,7576546102-7576769724,4104-5014,34-46,67594702-67751934,8541532888-8541668837,72-87,346340-480731,3358258808-3358456067,78265-98021,7969-9161,19293-27371,5143721-5316417,5641-7190,28793-36935,3232255123-3232366239,706-847,204915-242531,851-1135,790317-858666
diff --git a/02.lisp b/02.lisp
@@ -0,0 +1,30 @@
+(require "asdf")
+
+(defun day2-part1 (input-file)
+ (let* ((s (uiop:read-file-string input-file))
+ (u (uiop:split-string s :separator ","))
+ (tot 0))
+ (dolist (v u)
+ (let* ((w (uiop:split-string v :separator "-"))
+ (x (parse-integer (first w)))
+ (y (parse-integer (second w)))
+ (z (sum-invalids-in-range x y)))
+ (setf tot (+ tot z)) ))
+ tot))
+
+; I tried to be clever and step through just invalid numbers, but it's quite fiddly handling all the edge cases
+; let's see if the naive thing is fast enough
+(defun sum-invalids-in-range (start end)
+ (do ((x start (1+ x))
+ (tot 0))
+ ((> x end) tot)
+ (if (is-invalid x)
+ (setf tot (+ tot x)))))
+
+(defun is-invalid (x)
+ (let* ((y (write-to-string x))
+ (l (length y))
+ (m (floor l 2))
+ (n1 (subseq y 0 m))
+ (n2 (subseq y m)))
+ (equal n1 n2)))
+\ No newline at end of file
diff --git a/02.sample.input b/02.sample.input
@@ -0,0 +1 @@
+11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124
+\ No newline at end of file
