Split the array into three equal portions Sort each of these portions Merge the resulting lists
Let's consider a long, quiet country with houses scattered very sparsely along it. (We can picture the road as a long line segment with an eastern endpoint and a western endpoint.) Further, let's suppose that despite the bucolic setting, the residents of all these houses are avid cell phone users. You want to place cell phone base stations at certain points along the road, so that every house is within four miles of one of the base stations.