Subject: Analysis of Algorithms

There are N ants on top of a fallen log (imagine the log as a very long line segment, and ants as points on the line). Each ant i is at the location a_i (a real number) meters from the leftmost of the log. You want to get rid of the ants by placing traps on the log. Each trap will lure ants that are 2-meter distance away. Give an efficient Greedy Algorithm that will get rid of all of the ants with minimal number of traps.