function [b,rearranged_cols]=rearrange_cols(A)
%[b,rearranged_cols]=rearrange_cols(A)
%For examples and more details, please refer to the LDPC toolkit tutorial at
%http://arun-10.tripod.com/ldpc/ldpc.htm
%Rearrange the columns of the parity check matrix to get non singular A matrix

dim=size(A);
rows=dim(1);
cols=dim(2);
newA=A;
for i=1:rows
   rearranged_cols(i)=0;
end


for i=1:rows
   if newA(i,i)==0
      k=i+1;
      if k<cols
       %while A(rows,k)==0
         while newA(i,k)==0
            k=k+1;
         	if k==cols
               break
            end
         end 
         %if k~=cols
         temp=newA(1:rows,k);
         newA(1:rows,k)=newA(1:rows,i);
         newA(1:rows,i)=temp;
               
         rearranged_cols(i)=k;
               
         temp=A(1:rows,k);
         A(1:rows,k)=A(1:rows,i);
         A(1:rows,i)=temp;
         %end
     end
   end
   for j=1:rows
      if j~=i
          if newA(j,i)==1
             newA(j,1:cols)=xor(newA(i,1:cols),newA(j,1:cols));
          end 
      end
   end
   A;

end   

rearranged_cols;
   b=A;