% By Willi Mutschler, September 26, 2016. Email: willi@mutschler.eu
function p = uperm(a)
[u, ~, J] = unique(a);
p = u(up(J, length(a)));


function p = up(J, n)
ktab = histcounts(J,1:max(J));
l = n;
p = zeros(1, n);
s = 1;
for i=1:length(ktab)
    k = ktab(i);
    c = nchoosek(1:l, k);
    m = size(c,1);
    [t, ~] = find(~p.');
    t = reshape(t, [], s);
    c = t(c,:)';
    s = s*m;
    r = repmat((1:s)',[1 k]);
    q = accumarray([r(:) c(:)], i, [s n]);
    p = repmat(p, [m 1]) + q;
    l = l - k;
end
end

end % uperm