function [w,levels,ll] = treewidth(T)
[n,n] = size(T);
global LEVELS
LEVELS = repmat({[]},n,1);
getLevels(T,1,0);
w = 0;
ll = [];
for ell = 1:n
  w = max(w,length(LEVELS{ell}));
  if ~isempty(LEVELS{ell})
    ll(end+1)=length(LEVELS{ell});
  end
end
levels = LEVELS;
return


function getLevels(T,u,ell)
global LEVELS
ell = ell+1;
LEVELS{ell}(end+1) = u;
ukids = find(T(u,:));
for vi=1:length(ukids)
  v = ukids(vi);
  getLevels(T,v,ell);
end

return