matthiasm@8: function C = mysymsetdiff(A,B)
matthiasm@8: % MYSYMSETDIFF Symmetric set difference of two sets of positive integers (much faster than built-in setdiff)
matthiasm@8: % C = mysetdiff(A,B)
matthiasm@8: % C = (A\B) union (B\A) = { things that A and B don't have in common }
matthiasm@8: 
matthiasm@8: if isempty(A)
matthiasm@8:   ma = 0;
matthiasm@8: else
matthiasm@8:   ma = max(A);
matthiasm@8: end
matthiasm@8: 
matthiasm@8: if isempty(B)
matthiasm@8:   mb = 0;
matthiasm@8: else
matthiasm@8:   mb = max(B);
matthiasm@8: end
matthiasm@8: 
matthiasm@8: if ma==0 
matthiasm@8:   C = B;
matthiasm@8: elseif mb==0
matthiasm@8:   C = A;
matthiasm@8: else % both non-empty
matthiasm@8:   m = max(ma,mb);
matthiasm@8:   bitsA = sparse(1, m);
matthiasm@8:   bitsA(A) = 1;
matthiasm@8:   bitsB = sparse(1, m);
matthiasm@8:   bitsB(B) = 1;
matthiasm@8:   C = find(xor(bitsA, bitsB));
matthiasm@8: end