%T---TAIL,  H---HEAD
%DEGO---degree_out,    DEGI---degree_in
%N---number of nodes,  M---number of arcs
%A{i}---out-arc list at node i, cell array
%AI{i}---in-arc list at node i, cell array

DEGO=zeros(1,N);
DEGI=DEGO;
A{1,N} = [];
AI{1,N} = [];
for k=1:M
   i=T(k);
   j=H(k);
   pos=DEGO(i)+1;
   DEGO(i)=pos;
   A{i}(pos)=k;

   posI=DEGI(j)+1;
   DEGI(j)=posI;
   AI{j}(posI)=k;
end%for