From ab438d84d2892aa5e0be67f3f15029f5ce39ac07 Mon Sep 17 00:00:00 2001
From: Sijmen Schoon <me@sijmenschoon.nl>
Date: Sat, 1 Dec 2018 14:52:17 +0100
Subject: [PATCH] day1: add solution

---
 .gitignore |  1 +
 Day1A.hs   |  8 ++++++++
 Day1B.hs   | 14 ++++++++++++++
 3 files changed, 23 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Day1A.hs
 create mode 100644 Day1B.hs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..14140f4
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.in
diff --git a/Day1A.hs b/Day1A.hs
new file mode 100644
index 0000000..7a05045
--- /dev/null
+++ b/Day1A.hs
@@ -0,0 +1,8 @@
+module Day1A where
+
+read' :: String -> Integer
+read' ('+':str) = read str
+read' str = read str
+
+main :: IO ()
+main = interact $ show . sum . map read' . lines
diff --git a/Day1B.hs b/Day1B.hs
new file mode 100644
index 0000000..e9553fb
--- /dev/null
+++ b/Day1B.hs
@@ -0,0 +1,14 @@
+module Day1B where
+
+import Day1A (read')
+import qualified Data.Set as S
+
+handle :: Integer -> (S.Set Integer) -> [Integer] -> Integer
+handle freq history (nextDelta:xs)
+  | S.member freq history = freq  -- When the frequency is in the history set, return it
+  | otherwise             = handle (freq + nextDelta) (S.insert freq history) xs  -- Recurse otherwise
+handle _ _ _ = error "xs should not be empty :("
+
+main :: IO ()
+main = interact $ show . handle 0 S.empty . deltaFreqs
+  where deltaFreqs = cycle . map read' . lines  -- Convert input to Integers and repeat infinitely