Faster approximation for maximum independent set on unit disk graph

Abstract Maximum independent set from a given set D of unit disks intersecting a horizontal line can be solved in O ( n 2 ) time and O ( n 2 ) space. As a corollary, we design a factor 2 approximation algorithm for the maximum independent set problem on unit disk graph which takes both time and space of O ( n 2 ) . The best known factor 2 approximation algorithm for this problem runs in O ( n 2 log ⁡ n ) time and takes O ( n 2 ) space [1] , [2] .