day20.m

data = getData("input.txt");
IDs = cell2mat(data.keys);
IDs_cpy = IDs;
image = zeros(sqrt(length(IDs)));
ID1 = IDs(1);
tile = data(ID1);
x = 6;
y = 6;
image(x,y) = ID1;
newtiles = ID1;
finished = [];
while ~isempty(IDs_cpy)
    newnewtiles = [];
    for i = 1:length(newtiles)
        ID1 = newtiles(i);
        tile = data(ID1);
        IDs_cpy(ismember(IDs_cpy,finished)) = [];
        IDs_cpy(ismember(IDs_cpy,newnewtiles)) = [];
        %         disp(length(IDs_cpy));
        for j = 1:length(IDs_cpy)
            [x,y] = find(image == ID1);
            ID2 = IDs_cpy(j);
            if ID1 == ID2
                continue;
            end
            [edge1,edge2] = getMatch(ID1,ID2,data);
            if isempty(edge2)
                continue;
            end
            if edge2 == -1 || edge2 == -3
                data(ID2) = flipud(data(ID2));
                edge2 = -edge2;
            elseif edge2 == -2 || edge2 == -4
                data(ID2) = fliplr(data(ID2));
                edge2 = -edge2;
            end
            switch num2str([edge1,edge2])
                case {'1  1','3  3'}
                    data(ID2) = flipud(rot90(data(ID2),2));
                case {'2  2','4  4'}
                    data(ID2) = fliplr(rot90(data(ID2),2));
                case {'1  3','2  4','3  1','4  2'}
                case {'1  2','3  4'}
                    data(ID2) = flipud(rot90(data(ID2),1));
                case {'4  3','2  1'}
                    data(ID2) = fliplr(rot90(data(ID2),-1));
                case {'1  4','3  2'}
                    data(ID2) = rot90(data(ID2),-1);
                case {'2  3','4  1'}
                    data(ID2) = rot90(data(ID2),1);
                otherwise
                    error("oops" + num2str([edge1,edge2]));
            end
            switch edge1
                case 1
                    if y == length(image)
                        image_cpy = zeros(sqrt(length(IDs)));
                        image_cpy(:,1:end-1) = image(:,2:end);
                        image = image_cpy;
                        y = y-1;
                    end
                    image(x,y+1) = ID2
                case 2
                    if x == 1
                        image_cpy = zeros(sqrt(length(IDs)));
                        image_cpy(2:end,:) = image(1:end-1,:);
                        image = image_cpy;
                        x = 2;
                    end
                    image(x-1,y) = ID2
                case 3
                    if y == 1
                        image_cpy = zeros(sqrt(length(IDs)));
                        image_cpy(:,2:end) = image(:,1:end-1);
                        image = image_cpy;
                        y = 2;
                    end
                    image(x,y-1) = ID2
                case 4
                    if x == length(image)
                        image_cpy = zeros(sqrt(length(IDs)));
                        image_cpy(1:end-1,:) = image(2:end,:);
                        image = image_cpy;
                        x = x-1;
                    end
                    image(x+1,y) = ID2
            end
            newnewtiles = union(newnewtiles,ID2);
        end
        finished = union(finished,newtiles);
    end
    newtiles = setdiff(newnewtiles,finished);
end
part1 = uint64(image(1,1)*image(1,end)*image(end,1)*image(end,end))

bw = [];
for i = 1:numel(image)
    tile = data(image(i));
    tile = tile(2:end-1,2:end-1);
    [x,y] = ind2sub(size(image),i);
    x = x*8-7;
    y = y*8-7;
    bw(x:x+7,y:y+7) = tile;
end


nessie = logical([0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0;
    1,0,0,0,0,1,1,0,0,0,0,1,1,0,0,0,0,1,1,1;
    0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,1,0,0,0]);

part2 = 0;

turns = 0;
while turns <8
    turns = turns+1;
    for i = 1:size(bw,1)-2
        for j = 1:size(bw,2)-19
            if all((bw(i:i+2,j:j+19) & nessie) == nessie,'all')
                bw(i:i+2,j:j+19) = xor(bw(i:i+2,j:j+19),nessie);
            end
        end
    end
    if turns == 4
        bw = flip(bw);
    end
    bw = rot90(bw);
end
part2 = sum(bw,'all')

function [i,comp] = getMatch(ID1,ID2, data)
comp = [];
i = [];
tile1 = data(ID1);
up = tile1(1,:)';
down = tile1(end,:)';
left = tile1(:,1);
right = tile1(:,end);
edges1 = [right,up,left,down];
tile2 = data(ID2);
up = tile2(1,:)';
down = tile2(end,:)';
left = tile2(:,1);
right = tile2(:,end);
edges2 = [right,up,left,down];
for i = 1:4
    comp = find(all(edges1(:,i) == edges2));
    if comp
        return;
    end
end
edges2 = flipud(edges2);
for i = 1:4
    comp = find(all(edges1(:,i) == edges2));
    if comp
        comp = -comp;
        return;
    end
end
end

function data = getData(inputfile)
inp = string(strsplit(fileread(inputfile),"\n"))';
inp = strip(inp(1:end-1));
data = containers.Map('KeyType','double','ValueType','any');
for i = 1:11:length(inp)
    tile = inp(i+1:i+10);
    tile = strrep(tile,'#','a');
    tile = ~cell2mat(isstrprop(tile,'punct'));
    data(str2double(extractBetween(inp(i),' ',':'))) = tile;
end
end