$P$ versus $NP$ is considered as one of the most important open problems in computer science. This consists in knowing the answer of the following question: Is $P$ equal to $NP$? A precise statement of the $P$ versus $NP$ problem was introduced independently by Stephen Cook and Leonid Levin. Since that date, all efforts to find a proof for this problem have failed. A major complexity classes are $L$ and $\oplus L$. A logarithmic Turing machine has a read-only input tape, a write-only output tape, and some read/write work tapes. The work tapes may contain at most $O(\log n)$ symbols. $L$ is the complexity class containing those decision problems that can be decided by a deterministic logarithmic Turing machine. The complexity class $\oplus L...