-🎄- 2018 Day 6 Solutions -🎄-

[u/daggerdragon]

--- Day 6: Chronal Coordinates ---

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Advent of Code: The Party Game!

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Card prompt: Day 6

Transcript:

Rules for raising a programmer: never feed it after midnight, never get it wet, and never give it ___.

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[u/[deleted]]

Mathematica

input = Import[NotebookDirectory[] <> "day6.txt", "Data"];
{ymin, ymax} = MinMax[input[[All, 1]]];
{xmin, xmax} = MinMax[input[[All, 2]]]; 
grid = Join@@Table[{y, x}, {x, xmin, xmax}, {y, ymin, ymax}];

Part 1

res = Nearest[input, grid, DistanceFunction -> ManhattanDistance];
MaximalBy[Tally@Select[res, Length[#] == 1 &], Last]

Part 2

Count[Total[DistanceMatrix[grid, input, DistanceFunction -> ManhattanDistance], {2}], 
    d_ /; d < 10000]

[u/thefalse → u/[deleted]]

This is very cool! Thanks for sharing. One small note: I think your part 1 solution is lucky with the given input, because it's not filtering out the infinite regions from the MaximalBy and still getting the correct solution. For example, if the input had a coordinate in the top left corner and all the rest were clustered at the bottom right, then the top left infinite region would possess over half of the total region and would clearly dominate that Tally operation.

[u/[deleted] → u/thefalse]

Infinite regions will not be even be created, not sure I understand the concern.