$2$SAT. In the $2$SAT problem, you are given a set of clauses, where each clause is the disjunction

$($OR$)$ of two literals $($a literal is a Boolean variable or the negation of a Boolean variable$).$ You are looking

for a way to assign a value true or false to each of the variables so that all clauses are satisfied $$ that is$,$

there is at least one true literal in each clause. For example, here$$s an instance of $2$SAT with five clauses and

four variables