The perlish way is to just use LCSS; and let somebody else worry about how it works exactly. As far as the "without using bytes", why does that matter? Is this some kind of contrived CS undergrad assignment or something? Whether the solution uses bytes or not is an irrelevant detail of the implementation, something you would not, in any normal situation, ever care about.

Then you qualify your question with "that is efficient", but only a C programmer would ask that question without concrete evidence that the working implementation creates performance problems. Premature optimization is a root of all kinds of evil (for which some have strayed... and pierced themselves through with many sorrows). Get it working, get it working right, and only then worry about efficiency if it becomes a problem.