%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%     sp_dijkstra           %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% T,H are tail and head nodes of all arcs, COST is the cost vector.
% A{} are the out-arc cells initialized by netdata.

% s is the source node
s=input('give source node s:');

d=inf*ones(1,N);  % initialization
d(s)=0;

pred=zeros(1,N);
ULAB=1:N;         % ULAB--unlabelled set

while ~isempty(ULAB)
   [dmin,ind]=min(d(ULAB));
   
   i=ULAB(ind);
   ULAB=setdiff(ULAB,[i]);
   kk=A{i}; jj=H(kk);
   
   [d(jj), index]=min([d(jj); d(i)+COST(kk)']);         % we create a 2 by |jj| matrix
   pred(jj(find(index==2)))=i;                          % index =1 or 2, which records 
                                                        % the row-number that hits the minimum.
end%if

pred
d