function G = bipart(n)
n1 =  floor(n/2);
n2 =  ceil(n/2);

G = zeros(n);
for i=1:n1
  for j=1:n2
    % connect i to j
    G = connect(G,i,j,n1,n2);
  end
end
return


function G = connect(G,i,j,n1,n2)
ii = i;
jj = n1 + j;
G(ii,jj) = 1;
G(jj,ii) = 1;  
return