z10.m

function z10 (r)
    n=1;
    while ~r.is_mark
        b=kvadrat (r,n);
        if b==0
            break
        end
        n=n+2;
    end
end

function result=around_the_wall(r,u,v)
    count=0;
    while r.is_bord (v)
        r.step (u)
        count=count+1;
    end
    if ~ r.is_bord(v)
        r.step(v)
        result=true;
    else
        result=false;
    end
    while count>0
        r.step(invert (u))
        count=count-1;
    end
end


function s = invert (s)
    if s == 'w'
        s = 'o';
    elseif s == 'o'
        s = 'w';
    elseif s == 'n'
        s = 's';
    elseif s == 's'
        s = 'n';
    end
end


function y=kvadrat (r,n)
    y=1;
    for s = 'oswn'
        if s == 'o' || s == 'w'
            z = 'n';
        else
            z = 'o';
        end

        for k=1:n
            around_the_wall(r, z, s);
            if r.is_mark
                y=0;
                return
            end
        end
    end
    around_the_wall(r, 'n', 'w');
    around_the_wall(r, 'w', 'n');
end