solve: day 1, part 2

2020/01/README.md

@@ -1 +1,21 @@
 # Day 1
+
+## Part 1
+
+Took some time to remember how to read input.
+
+I assumed that I could build the list of pairs from
+the start and never tracing back (order doesn't matter).
+
+## Part 2
+
+Have to take the previous solution and deal with combinations of three values.
+
+Hardest part is figuring out how to take a list of numbers and return a list
+of 3 tuples for the combinations of pairs:
+
+```hs
+triples xs = sequence $ replicate 3 xs
+```
+
+This produces some additional data but I assume these entries won't be false positives.

2020/01/part2.hs

@@ -0,0 +1,24 @@
+#!/usr/bin/env runghc
+
+import Data.List
+import Data.Maybe
+
+main :: IO ()
+main =
+  do
+    input <- getInput
+
+    let answer = product $ fromJust $ find isSolutionTriple $ triples input
+
+    putStrLn $ show answer
+
+getInput :: IO [Int]
+getInput = fmap (map read . lines) getContents
+
+triples :: [a] -> [[a]]
+triples xs = sequence $ replicate 3 xs
+
+isSolutionTriple :: [Int] -> Bool
+isSolutionTriple triple = sum triple == 2020
+
+multplyTriple (a, b, c) = a * b * c