advent-of-code/2021/nim/day20.nim

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Nim
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import ./common, std/[sequtils, algorithm, sugar, sets, strformat, strutils, tables, options, json, hashes]
type
Point = (int, int)
Image = object
pixels: TableRef[Point, bool]
topLeft: Point
bottomRight: Point
infinite: bool
proc parse(s: openArray[string]): Image =
var pixels = newTable[Point, bool]()
for y,l in s.pairs:
for x,c in l:
pixels[(x, y)] = c == '#'
return Image(topLeft: (0, 0), bottomRight: (s[0].len-1, s.len-1), pixels: pixels, infinite: false)
proc enhance(image: var Image, algo: string) =
var (tlx, tly) = image.topLeft
var (brx, bry) = image.bottomRight
var newPixels = newTable[Point, bool]()
var xr = tlx-1..brx+1
var yr = tly-1..bry+1
for x in xr:
for y in yr:
var sample = 0
for sy in y-1..y+1:
for sx in x-1..x+1:
if image.pixels.getOrDefault((sx, sy), image.infinite):
inc sample
sample = sample shl 1
sample = sample shr 1
# echo &"{x}, {y} => {sample}"
newPixels[(x, y)] = algo[sample] == '#'
if x < tlx: tlx = x
if y < tly: tly = y
if x > brx: brx = x
if y > bry: bry = y
image.topLeft = (tlx, tly)
image.bottomRight = (brx, bry)
image.pixels = newPixels
if image.infinite:
image.infinite = algo[^1] == '#'
else:
image.infinite = algo[0] == '#'
proc `$`(image: Image): string =
var s: seq[string] = @[]
var (tlx, tly) = image.topLeft
var (brx, bry) = image.bottomRight
for _ in tly..bry:
s.add ".".repeat((brx-tlx)+1)
for p in image.pixels.keys:
let (x, y) = p
if image.pixels[p]: s[y-tly][x-tlx] = '#'
s.join("\n")
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proc solver(input: Lines, times: int): uint64 =
let algo = input[0]
var image = input[2..^1].parse()
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for _ in 1..times: image.enhance algo
for v in image.pixels.values:
if v: inc result
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proc p1(input: Lines): uint64 = input.solver(2)
proc p2(input: Lines): uint64 = input.solver(50)
const input = """
..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#
#..#.
#....
##..#
..#..
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..### """.strip().split('\n')
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doDayX 20, (n: int) => n.loadInput, p1, p2, (input, 35'u64, 3351'u64)