Day 2

README.md

@@ -7,3 +7,4 @@ My solutions to advent of code problems in 2024
 Below are a list of the programming languages used to solve each day:
 
 Day 1 - Haskell
+Day 2 - Haskell

day2/Lib.hs

@@ -0,0 +1,24 @@
+module Lib where
+
+import Data.List (delete)
+
+parsedFileString fileString = [[read word :: Int | word <- words line] | line <- lines fileString]
+
+getDiffs :: [Int] -> [Int]
+getDiffs report = [xiplus1 - xi | (xiplus1, xi) <- zip report (tail report)]
+
+checkReport :: [Int] -> Bool
+checkReport reports =
+  (all (> 0) diffs || all (< 0) diffs)
+    && all (\x -> let absX = abs x in absX > 0 && absX < 4) diffs
+  where
+    diffs = getDiffs reports
+
+-- This is a non-ideal brute-force approach but don't have time to improve
+checkReportDampened :: [Int] -> Bool
+checkReportDampened reports =
+  checkReport reports
+    || let reportSubsets = [checkReport (take n reports ++ drop (n + 1) reports) | n <- [0 .. (length reports)]]
+        in or reportSubsets
+
+getSafeReportCount checkFun = foldr ((+) . fromEnum . checkFun) 0

day2/README.md

@@ -0,0 +1,13 @@
+# Day 1
+
+## Instructions
+
+From this directory open a terminal and execute:
+
+```sh
+runhaskell day2.hs
+```
+
+The solution for each section will be printed to the terminal output.
+
+## Notes

day2/day2.hs

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+import Lib (checkReport, checkReportDampened, getSafeReportCount, parsedFileString)
+
+main = do
+  inputs <- readFile "inputs.txt"
+  let parsedInputs = parsedFileString inputs
+  let count = getSafeReportCount checkReport parsedInputs
+  putStrLn "The solution to part 1 is: "
+  print count
+  let count = getSafeReportCount checkReportDampened parsedInputs
+  putStrLn "The solution to part 2 is: "
+  print count