% encode as MacKay
function [H]=construction(h);
[m,n]=size(h);
%%% m   denote the number of column M
%%% n the number of 1 in each row 
%%% we only consider the R=0.5 matrix
H=zeros(m/2,m);
for i=1:m,
    for j=1:n,
        H(h(i,j),i)=1;
    end
end