停车场里经常碰到车对车的情况，有时候车停的还很深。这能最大化地增加停车场停的车的数量，但是车主的车被停在一大排的车后面。在这种情况下，所有的车要离开来让要出去的车离开-Parking lot attendants often park cars bumper-to-bumper, several cars deep. This maximizes the number of cars they can fit into a parking lot at the expense of complicating the process of retrieving someone s car when they want to leave. Consider the case of a person wanting to leave the parking lot but their car is parked in the back of a row of cars. In this case, all the cars parked in front of this person s car must be temporarily moved to allow this person to leave.