再例： SATISFIABILITY PROBLEM. SAT={wwis a code of a satisfiable formula in CNF) CLIQUE PROBLEM CLIQUE={x#w∈{0，l,#}*|x∈{0，l}*and w represents a graph that contains a clique of size Number(x). VERTEX COVER PROBLEM Formally,the vertex cover problem (VCP)is the decision problem (VCP,10,1,#),where VCP={u#w∈{0，l,#}+|u∈{0，l}+and w represents a graph that contains a vertex cover of size Number(u)再例：