wolffd@0: function C = mysymsetdiff(A,B)
wolffd@0: % MYSYMSETDIFF Symmetric set difference of two sets of positive integers (much faster than built-in setdiff)
wolffd@0: % C = mysetdiff(A,B)
wolffd@0: % C = (A\B) union (B\A) = { things that A and B don't have in common }
wolffd@0: 
wolffd@0: if isempty(A)
wolffd@0:   ma = 0;
wolffd@0: else
wolffd@0:   ma = max(A);
wolffd@0: end
wolffd@0: 
wolffd@0: if isempty(B)
wolffd@0:   mb = 0;
wolffd@0: else
wolffd@0:   mb = max(B);
wolffd@0: end
wolffd@0: 
wolffd@0: if ma==0 
wolffd@0:   C = B;
wolffd@0: elseif mb==0
wolffd@0:   C = A;
wolffd@0: else % both non-empty
wolffd@0:   m = max(ma,mb);
wolffd@0:   bitsA = sparse(1, m);
wolffd@0:   bitsA(A) = 1;
wolffd@0:   bitsB = sparse(1, m);
wolffd@0:   bitsB(B) = 1;
wolffd@0:   C = find(xor(bitsA, bitsB));
wolffd@0: end