advent-of-code/2021
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Day 20 solution

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I would have had this done last night, but... _unintelligible muttering about key[0] being '#' in the real input and '.' in the sample...

Day 19 is...still vexing me. Maybe I'll get back to it later.
This commit is contained in:
Chris Pickett
2021-12-20 09:09:43 -06:00
parent fd1a93fa10
commit 8a33549ad2
4 changed files with 221 additions and 1 deletions
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3
advent-of-code-2021.csproj
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@ -72,6 +72,9 @@
<None Update="inputs\18.txt">
<CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
</None>
<None Update="inputs\20.txt">
<CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
</None>
</ItemGroup>
</Project>

102
inputs/20.txt Normal file
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@ -0,0 +1,102 @@
###.#####..###..###.....##.##.#..#.#######..#...####.....#.#.###..##.#....####.#...##.#.#..##.###..######.#.#.#.##..#...##..###....####.##.##..#.#..##...##.#..#..#...#..#....###.####.######..#..#..#..#..........#.####...#..####.##.....#.#..#..#..####.##..#...####..#....#...##.#####...##.#.##.#..#....###....###..#...#....###.#....#..##....#..#..#..#..#.......###..##..##..####...###..#.....######.#.#.#.####.####.#####.....#..#...#.#.###...#...#.##.##.....#....#..##.###..#.##.#.##..#.#......####.#....#..#.#...
...#.####...#...#..#####..#.#.##........###..#.....##..####.###.#####......#.##.#..###.#####..#..###
#...#.#....####.##.#...###..##...#.###...###...#..#.##.#.###..#.#.##..#.####.#..#..#.####.##.#..#...
....#.##..##.#####.#...#########..#.#.####....#..#.#..##.##.###.#.####.##.###.##...#.######..#.#.#..
..#.##.###.##..#.###..#.#..#.#..###..........#..#..###.#.......###.##.#.#..#####.##.###.###.###..#.#
##...#...#.###.#####..#.#####.#..##.#.##.#..#.##.#..#...##...####.#.#..#....#########.#.##...####.##
###.##...#.###...#.####...#.#.##..##......##..#.###..#####..##...##.##..##..##.##...#.#.#..#.#..##..
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###..##.####..####.#.##..#..#.######.#.#####....#..#.#......#........#.#..##.#.####...###.#..#.##..#
.##.#.####.#.##.###..#..#....#####.#.....#..#....###.....#.#..######..#..#....#.##....####.###.#.##.
.#..#.....##....#.#.#...######...####.#####..#.#.#.##.#..#####.#.#.#.##..#..##.##.......##..#.#.##..
###..##...####....##.#...#..##.##.###.#......##...##.....#.#.#.....#.###.##..####..##.####.#.###.###
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##.###.###....########....#.#...###..#.##.#....###..#.#.....###..#.#..#.##.#.......######.#.#.##....
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.#.######.##.#..#..###.#.###..#.#.#..#...#..##.#######.#...#...#..####.#....###...#.###.##...##....#
.#.##.#.#.#..#..#.####.##..####..#..###.#.##..#..##........#.#.#.#########.#..####..#..#.##.##....#.
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...#.#...#....##.#....##.##.##.#.#..#.##.#.###.#.#.#.#.#######.#.##.##..#..##.#.....#..##..#.##.#...
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.#....##..##..#..#...##.##.#.##..#.##.#.#...#####..#....##...##...#...####.###.#..#####.#..##..#..##
###.#####.#.#...#.#.#######.#.....#####.#...#..#.##.###...#..#..#.#..##..#.#...###.##.#..##..###.#.#
.#####.###.#######..#.#......#.##.#.##.#.#...##....##.#.#.#...#..#....##...#..#...#...###....#..#.##
###...##.##.##.##..####.##.######.#.######.##..#.#...##...#....####...#..##....#..#..#####....#.#..#
#...###.#.#.###...####...##.#.#..###..#######.##.####..#.####..##.#.##.###.######.........###.#.#.##
####.###.#.#.#.####...#..#..######.#..####..##.#.###...#.#.#.##....#..#.#.##.#..#....#...##.##..###.
#...#..##.#...#..##..##.####.#..###.##.#...#.#.#...##.##.#.#....##...###.#...#...#..#.#.#.##.##....#
...#...###...#..######.#.####.#.#..####.....#.####..###.#.######..##.......##.#...#..##..#.###..###.
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##...####.##.##...#.###...##..#.##..#.##...####..###.....#.##.#.##.#.#....###.........#.#.#..###.###
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###.#..##.#...####..##..##.#...#.##..#..##.####.#..#.#.#..#.##....#..#......###....####......#.#...#
.#######...###...###.##.#.#..#.....##...#...#.####..##.#.##..#.#...#..###........##..##.#.##..#.....
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.#..#.#..#...#.#.#..#..#..###..#####..###.#.#.####.##..#.#....####.##...#...#....##..##.##...###.#.#
.#.##..#######..#.......#.###..#.#.###.#..##.##......##.####.##.###......#.###.#.#...#...##.....##..
#..####.....#..#...###.#.###..#...#.###.#...###...##.##....##.##..#.###.###.###.#.##...####.#.##.##.
.###.....#####.##.#...####..#.##..###########..#...######.......###.......####.###....#.###.....###.
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.....#.#...#...#.###..#..#.#....#....#..#.###.##.#.##.##..#.#.....#.###....####.#....#.....#.#..#.##
#...#.##..#.#..##.#.....#.#.#.#..#.####..#...#.#.#...##.....#.#####..##..##..###.##.#....#.....#....
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#.###.#.#.###.#.#.#..##.#..#.######..#...#....#..###.##.#...#.#.#.#.####....##..###.###....#.#.###..
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###..#.#..###..#..##..###.....#####.#.#...#.##......#.#.#........#.#...#.....##..##...#.#....#.#..#.
##....#####...#.#..###.####...#...##....##..#.#...#...##.##...##........#.#....#####..#.....####..#.
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##..#..#...#..##...#.#.##...#....##..#.#.##.....##.#####.##..##....#.#......#.###.....#.###.....#...
#.#.#..#..##...#.##.##.###.###......#...###....#.#..##..#.##..#..#.##.#####...#...###.#####..#...###
...#..##.######.#..#..##..#..##..#....#.#.#..#...#.##....##.#.##.##....###.#.######..#..###...##.#..
###...######..#.##.##.#.#.###.#.#.#...###.##...##.#.##.#.#.#..#....####...###.#..##.##.#.##..#..#..#
#.##..###.######..#..#.##.##.#.##..##..#.##..#.##..##.######.#.#....#.#...#...##..#.#.##.#.#...#.#.#
..##.#.#...###.##.....#.#.#.#.#####..###.#..##..##.#.#..##.#.###..#..#.##....#....##...#######.#.#.#
.#.###.....#..#.#.....#..#.....#....#....##..###.##.##.#.#####....#.####.....##....#.####.#.##...##.
#.####.##..#..#....###.#.......####..##.##..##...#...#..##..##.#...#.#..#..#.##.##.#..########..####
.###.#.#..#######...#.#.###.#.#.##.....#.#..##.#..##..#.#....##..##..##..##.#.#.#..#.#..#.#...#..#..
###.#.#.#....#.#..#..###..#..#.####.#.#....#.#####..#.####.#.##.#######.##...###.#...#..#.####..###.
.#.....###.##.##..#..###...####....####...#..#...###..##...##.###.###..#.##.#.#.####.....##.#.......
.#..##.#.#...##.#..........##.####.#.###..##....#.....#.####........#.#.#.##.##.##.#...##..#..###...
#.#.###.###..#.##..#.##..##...#..#.......####...#.#..#...##.#.##...#..##.###.####.#......#.......###
..###..#..####.#.#...#..###..#.#.#...#####..#..#####..#.......#.#..#.###..#..#.##.######.###.#.#..#.
#.###.##.#..#...##.#.##.##..###.#.#.#..#.....#..##..#...#.#####.#.#.#.........#.#####.#..#####...#.#
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#...##.###..#.#...##.##...##..#..#.#.##.#.#..####..#####...##.##.####...#.###.#.##...##...#.##.##.##
#.##..###..###.#...#.....#...##...#..##.##.#..##...###.#.....#.##.......#####.#####....#.###.#######
..#...##.#..####...###..#.##...#.##.#.....##..##...#.#..#.#.#.##.......#...#.###..#....##.######....
###.#..###..##.#........##.#.#.#..#....##.#...#....#.###..##.##.##.###..####.#####.....##...#..#.##.
.####.##.....##............##.#...##.###...#.##..########.#..###......##..##.##..##..#.###....#.##..
##.##.##.#..#...########.####.####.#.#.###..#...#.#.###..##.#.#.####.#..#.#.....#..#..##.#..##.##...
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##.##.#..##....#.######..##...#.##.#...#.#.####..####.##...####.#.#.#.##.#....###..##.#######..#..#.
.....##....#.##.##.#.##....#.#.##.##......####.##..##.#....#..#.##.###.#..#....##.#..#.#.#.#.##...#.
.#.#..#...#..#..#.....#####...#####..##.#.##.#.#....##..##............#.##...######..#.###..#...#..#
#.#####.##.#.#.....#...#..#.#.#....#....#..##.#..#..#....####.#...#.##.####.#.##.#...#.#.#.#..#...##

114
src/20.cs Normal file
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@ -0,0 +1,114 @@
namespace aoc2021;
internal class Day20 : Day
{
internal override void Go()
{
var lines = Util.ReadAllLines("inputs/20.txt");
string key = lines.ElementAt(0);
var grid = new List<List<byte>>(lines.ElementAt(2).Length);
for (int i = 2; i < lines.Count(); i++)
{
var line = lines.ElementAt(i);
var row = new List<byte>(line.Length);
grid.Add(row);
line.ForEach(ch => row.Add(ch switch
{
'#' => 1,
_ => 0,
}));
}
Part1(grid, key);
Part2(grid, key);
}
private static void Part1(List<List<byte>> grid, string key)
{
int numLit = grid.Sum(row => row.Count(col => col == 1));
using var t = new Timer();
(grid, numLit) = Enhance(grid, key);
(grid, numLit) = Enhance(grid, key);
t.Stop();
Logger.Log($"<+black>> part1: #lit=<+white>{numLit}<r>");
}
private static void Part2(List<List<byte>> grid, string key)
{
using var t = new Timer();
int numLit = 0;
for (int i = 0; i < 50; i++)
{
(grid, numLit) = Enhance(grid, key);
}
t.Stop();
Logger.Log($"<+black>> part2: #lit=<+white>{numLit}<r>");
}
private static bool IsValidIdx(int len, int idx) => idx >= 0 && idx < len;
private static (List<List<byte>> grid, int numLit) Enhance(List<List<byte>> grid, string key)
{
var newSize = grid.Count + 2;
var emptyRow = Enumerable.Range(0, newSize).Select(_ => (byte)0);
var outImg = new List<List<byte>>(newSize);
for (int rowIdx = 0; rowIdx < newSize; rowIdx++)
{
outImg.Add(new List<byte>(emptyRow));
}
var def = key[0] == '#' && grid.Count % 4 != 0 ? '1' : '0';
int numLit = 0;
for (int row = - 1; row < grid.Count + 1; row++)
{
for (int col = - 1; col < grid.Count + 1; col++)
{
var num = Enumerable.Range(0, 9).Select(_ => def).ToArray();
if (IsValidIdx(grid.Count, row - 1))
{
if (IsValidIdx(grid.Count, col - 1))
num[0] = (char)(grid[row - 1][col - 1] + '0');
if (IsValidIdx(grid.Count, col))
num[1] = (char)(grid[row - 1][col] + '0');
if (IsValidIdx(grid.Count, col + 1))
num[2] = (char)(grid[row - 1][col + 1] + '0');
}
if (IsValidIdx(grid.Count, row))
{
if (IsValidIdx(grid.Count, col - 1))
num[3] = (char)(grid[row][col - 1] + '0');
if (IsValidIdx(grid.Count, col))
num[4] = (char)(grid[row][col] + '0');
if (IsValidIdx(grid.Count, col + 1))
num[5] = (char)(grid[row][col + 1] + '0');
}
if (IsValidIdx(grid.Count, row + 1))
{
if (IsValidIdx(grid.Count, col - 1))
num[6] = (char)(grid[row + 1][col - 1] + '0');
if (IsValidIdx(grid.Count, col))
num[7] = (char)(grid[row + 1][col] + '0');
if (IsValidIdx(grid.Count, col + 1))
num[8] = (char)(grid[row + 1][col + 1] + '0');
}
var keyIdx = Convert.ToInt32(new string(num), 2);
var ch = (byte)(key[keyIdx] == '#' ? 1 : 0);
outImg[row + 1][col + 1] = ch;
if (ch == 1)
{
numLit++;
}
}
}
return (outImg, numLit);
}
}

3
src/main.cs
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@ -36,7 +36,8 @@ else
"15" => new Day15(),
"16" => new Day16(),
"17"=> new Day17(),
_ => new Day18(),
"18" => new Day18(),
_ => new Day20(),
};
day.Go();
}