From d040b97bc8186b4ed261c901e770eccb2a3cc885 Mon Sep 17 00:00:00 2001
From: Xavier Morel <xavier.morel@cybelangel.com>
Date: Sun, 10 Jan 2021 10:47:08 +0100
Subject: [PATCH] Add 2020 day 25 p1

---
 haskellAoC/inputs/2020/25     |  2 ++
 haskellAoC/src/Y2020/Day25.hs | 18 ++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 haskellAoC/inputs/2020/25

diff --git a/haskellAoC/inputs/2020/25 b/haskellAoC/inputs/2020/25
new file mode 100644
index 0000000..19182ea
--- /dev/null
+++ b/haskellAoC/inputs/2020/25
@@ -0,0 +1,2 @@
+3418282
+8719412
diff --git a/haskellAoC/src/Y2020/Day25.hs b/haskellAoC/src/Y2020/Day25.hs
index 77600cf..d517c90 100644
--- a/haskellAoC/src/Y2020/Day25.hs
+++ b/haskellAoC/src/Y2020/Day25.hs
@@ -1,6 +1,20 @@
 module Y2020.Day25 (y20day25) where
 
+doTransform :: Int -> Int -> Int
+doTransform subjNumber n = rem (n * subjNumber) 20201227
+
+getLoopSize :: Int -> Int
+getLoopSize targetPK = length $ takeWhile (/= targetPK) $ iterate (doTransform 7) 1
+
+transformNtimes :: Int -> Int -> Int
+transformNtimes subjNumber loopSize = head $ drop loopSize $ iterate (doTransform subjNumber) 1
+
 y20day25 :: [String] -> (String, String)
 y20day25 input = (part1, part2)
-  where part1  = "WIP"
-        part2  = "WIP"
+  where part1  = show $ transformNtimes doorpk cardls
+        part2  = show $ "WIP"
+        input' = map read input :: [Int]
+        doorpk = input' !! 0
+        cardpk = input' !! 1
+        -- doorls = getLoopSize doorpk
+        cardls = getLoopSize cardpk