AdventOfCode/2020/13_haskell.ipynb

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{
"cells": [
{
"cell_type": "code",
"execution_count": 1,
"metadata": {},
"outputs": [],
"source": [
"puzzle <- readFile \"13.txt\"\n",
"plines = lines puzzle"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Day 13"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Puzzle 1"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"1835"
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"import Data.List.Split\n",
"\n",
"target = read $ head plines :: Int\n",
"nums = map read $ filter (/=\"x\") $ splitOn \",\" $ last plines :: [Int]\n",
"\n",
"let (t, n) = minimum [((target `div` n + 1) * n - target, n) | n <- nums]\n",
" in t * n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Puzzle 2"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {},
"outputs": [
{
"data": {
"text/plain": [
"247086664214628"
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"extendedGcd :: Int -> Int -> (Int, Int, Int)\n",
"extendedGcd 0 b = (b, 0, 1)\n",
"extendedGcd a b = (g, y - (b `div` a) * x, x)\n",
" where (g, x, y) = extendedGcd (b `mod` a) a\n",
"\n",
"chineseRemainder :: [Int] -> [Int] -> Int\n",
"chineseRemainder n a = sum [ai * x * p | (ni, ai) <- zip n a, let p = prod `div` ni; (_, x, _) = extendedGcd p ni] `mod` prod\n",
" where prod = product n\n",
"\n",
"nums = [(read x, i) | (x, i) <- zip (splitOn \",\" $ last plines) [0..], x /= \"x\"] :: [(Int, Int)]\n",
"\n",
"let n = map fst nums\n",
" a = map (uncurry (-)) nums\n",
" in chineseRemainder n a"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Haskell",
"language": "haskell",
"name": "haskell"
},
"language_info": {
"codemirror_mode": "Haskell",
"file_extension": ".hs",
"mimetype": "text/x-haskell",
"name": "haskell",
"pygments_lexer": "Haskell",
"version": "8.8.4"
}
},
"nbformat": 4,
"nbformat_minor": 4
}