From a7e4737b00a713ba9a4c793d3950317d0d56c326 Mon Sep 17 00:00:00 2001
From: Xavier Morel <xavier.morel@cybelangel.com>
Date: Thu, 10 Dec 2020 17:23:43 +0100
Subject: [PATCH] Add 2020 day 10

---
 haskellAoC/inputs/2020/10     | 93 +++++++++++++++++++++++++++++++++++
 haskellAoC/src/Y2020/Day10.hs | 19 +++++++
 haskellAoC/src/Y2020/Days.hs  |  2 +
 3 files changed, 114 insertions(+)
 create mode 100644 haskellAoC/inputs/2020/10
 create mode 100644 haskellAoC/src/Y2020/Day10.hs

diff --git a/haskellAoC/inputs/2020/10 b/haskellAoC/inputs/2020/10
new file mode 100644
index 0000000..6a9eb2f
--- /dev/null
+++ b/haskellAoC/inputs/2020/10
@@ -0,0 +1,93 @@
+80
+87
+10
+122
+57
+142
+134
+59
+113
+139
+101
+41
+138
+112
+46
+96
+43
+125
+36
+54
+133
+17
+42
+98
+7
+114
+78
+67
+77
+28
+149
+58
+20
+105
+31
+19
+18
+27
+40
+71
+117
+66
+21
+72
+146
+90
+97
+94
+123
+1
+119
+30
+84
+61
+91
+118
+2
+29
+104
+73
+13
+76
+24
+148
+68
+111
+131
+83
+49
+8
+132
+9
+64
+79
+124
+95
+88
+135
+3
+51
+39
+6
+60
+108
+14
+35
+147
+89
+34
+65
+50
+145
+128
diff --git a/haskellAoC/src/Y2020/Day10.hs b/haskellAoC/src/Y2020/Day10.hs
new file mode 100644
index 0000000..8a247ab
--- /dev/null
+++ b/haskellAoC/src/Y2020/Day10.hs
@@ -0,0 +1,19 @@
+module Y2020.Day10 (y20day10) where
+
+import Data.List
+
+sliding :: [Int] -> [(Int, Int)]
+sliding (x1:x2:xs) = ((x1, x2):(sliding (x2:xs)))
+sliding (x1:[]) = ((x1, x1+3):[])
+sliding [] = []
+
+combinations :: Int -> Int
+combinations n = nb !! n
+  where nb = [1, 1, 2, 4, 7, 13]
+
+y20day10 :: [String] -> (String, String)
+y20day10 input = (part1, part2)
+  where part1 = show $ product $ map length $ group $ filter (/= 2) $ sort $ diffs
+        part2 = show $ product $ map (combinations . length) $ filter (\(x:_) -> x /= 3) $ group $ diffs
+        input' = sort $ map read input :: [Int]
+        diffs = map (\(a, b) -> b - a) $ (0, head input'):(sliding input')
diff --git a/haskellAoC/src/Y2020/Days.hs b/haskellAoC/src/Y2020/Days.hs
index ce7db2d..45e2acb 100644
--- a/haskellAoC/src/Y2020/Days.hs
+++ b/haskellAoC/src/Y2020/Days.hs
@@ -9,6 +9,7 @@ import Y2020.Day06
 import Y2020.Day07
 import Y2020.Day08
 import Y2020.Day09
+import Y2020.Day10
 
 year2020 :: String -> [String] -> (String, String)
 year2020 "01" = y20day01
@@ -20,3 +21,4 @@ year2020 "06" = y20day06
 year2020 "07" = y20day07
 year2020 "08" = y20day08
 year2020 "09" = y20day09
+year2020 "10" = y20day10