ABSTRACT
Restriction is one of the most basic techniques to design approximation algorithms. The idea is to generate a solution to a given problem P by providing an optimal or suboptimal solution to a subproblem of P . By a subproblem of a problem P we mean restricting the solution space for P by disallowing a subset of the feasible solutions. The most common approach is to solve one subproblem, but there are algorithms that first solve several subproblems and the algorithm outputs the best of these solutions. An optimal or suboptimal solution to the subproblem(s) is generated by any of the standard methodologies.
