From bd66e14d3d10d863e19fc767f9d1c612d6b5f8ed Mon Sep 17 00:00:00 2001
From: Jordan Doyle <jordan@doyle.la>
Date: Wed, 6 Dec 2023 00:54:51 +0000
Subject: [PATCH] Add day 1

---
 1.hs | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100755 1.hs

diff --git a/1.hs b/1.hs
new file mode 100755
index 0000000..1676ab4
--- /dev/null
+++ b/1.hs
@@ -0,0 +1,68 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i runghc -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ ])"
+import Data.List (find, isInfixOf)
+import Data.Maybe (catMaybes)
+
+{- https://adventofcode.com/2023/day/1 -}
+
+main = print =<< run 0
+
+-- recursively read each line from stdin, concatenating first and last digits and folding the result into a sum
+run :: Int -> IO Int
+run acc = do
+  line <- getLine
+  if null line
+    then return acc
+    else do
+      let x = concatFirstLastDigitsInString line
+      run $ acc + x
+
+-- read first and last digit in a string and concatenate the two together
+concatFirstLastDigitsInString :: String -> Int
+concatFirstLastDigitsInString s =
+  case catMaybes [findDigitFromLeft "" s, findDigitFromRight "" s] of
+    [x, y] -> x * 10 + y
+    [x] -> x * 11
+    _ -> 0
+
+-- find the first digit in the string, searching from the left hand side
+findDigitFromLeft :: String -> String -> Maybe Int
+findDigitFromLeft acc "" = findDigit acc
+findDigitFromLeft acc (x : xs) = case findDigit acc of
+  Just v -> Just v
+  Nothing -> findDigitFromLeft (acc ++ [x]) xs
+
+-- find the last digit in the string, searching from the right hand side
+findDigitFromRight :: String -> String -> Maybe Int
+findDigitFromRight acc "" = findDigit acc
+findDigitFromRight acc xs = case findDigit acc of
+  Just v -> Just v
+  Nothing -> findDigitFromRight (last xs : acc) (init xs)
+
+-- finds a digit in either textual or numeric form and returns it as an int
+findDigit :: String -> Maybe Int
+findDigit s = case find (`isInfixOf` s) digitAsText of
+  Just textual -> lookup textual digitMap
+  Nothing -> Nothing
+  where
+    digitMap =
+      [ ("eight", 8),
+        ("seven", 7),
+        ("three", 3),
+        ("nine", 9),
+        ("four", 4),
+        ("five", 5),
+        ("two", 2),
+        ("one", 1),
+        ("six", 6),
+        ("1", 1),
+        ("2", 2),
+        ("3", 3),
+        ("4", 4),
+        ("5", 5),
+        ("6", 6),
+        ("7", 7),
+        ("8", 8),
+        ("9", 9)
+      ]
+    digitAsText = map fst digitMap
--
libgit2 1.7.2