day24_matrix.m

tic
tiles = getData('input.txt');
part1 = sum(groupcounts(tiles)==1)
un = unique(tiles);
tiles = un(groupcounts(tiles) ==1);
grid = zeros(250,250);
for i = 1:length(tiles)
    grid(real(tiles(i))+125,imag(tiles(i))+125) = 1;
end
spy(grid);
for k = 1:100
    grid = generation(grid);
    spy(grid);
end
part2 = nnz(grid)
toc
function [nextgrid] = generation(grid)
directions = [2;-2;1-1i;-1-1i;-1+1i;1+1i];
nextgrid = zeros(250,250);
[tilesX,tilesY] = ind2sub(size(grid),find(grid));
tiles = complex(tilesX-125,tilesY-125);
    for i = 1:length(tiles)
        n = 0;
        tile = tiles(i);
        neighbors = tile+directions;
        for j = 1:6
            if grid(real(neighbors(j))+125,imag(neighbors(j))+125) == 1
                n = n+1;
            else
                m = 0;
                grand_neighbors = neighbors(j)+directions;
                for k = 1:6
                    if grid(real(grand_neighbors(k))+125,imag(grand_neighbors(k))+125) == 1
                        m = m+1;
                    end
                end
                if m == 2
                    nextgrid(real(neighbors(j))+125,imag(neighbors(j))+125) = 1;
                end
            end
        end
        if n > 0 && n <= 2
            nextgrid(real(tile)+125,imag(tile)+125) = 1;
        end
    end
end

function data = getData(inputfile)
inp = string(strsplit(fileread(inputfile),"\n"))';
inp = strip(inp(1:end-1));
data = zeros(length(inp),1);
dirs = ["se","sw","nw","ne","w","e"];
for i = 1:length(inp)
    for j = 1:length(dirs)
        c = count(inp{i},dirs{j});
        inp{i} = erase(inp{i},dirs{j});
        switch dirs{j}
            case "e"
                data(i) = data(i) + c*2;
            case "w"
                data(i) = data(i) - c*2;
            case "se"
                data(i) = data(i) + c*(1-1i);
            case "sw"
                data(i) = data(i) + c*(-1-1i);
            case "nw"
                data(i) = data(i) + c*(-1+1i);
            case "ne"
                data(i) = data(i) + c*(1+1i);
        end
    end         
end
end