设有一个可以停放n辆汽车的狭长停车场,它只有一个大门可以供车辆进出。车辆按到达停车场时间的早晚依次从停车场最里面向大门口处停放(最先到达的第一辆车放在停车场的最里面)。如果停车场已放满n辆车,则后来的车辆只能在停车场大门外的便道上等待,一旦停车场内有车开走,则排在便道上的第一辆车就进入停车场。停车场内如有某辆车要开走,在他之后进入停车场的车都必须先退出停车场为它让路,待其开出停车场后,这些车辆在依原来的次序进场(There is a long and narrow parking lot for n cars. It has only one gate to get in and out of the car. Vehicles are parked from the inside of the parking lot to the gate at the end of the parking lot (the first car first arrives at the bottom of the parking lot). If the parking lot is full of N cars, the later vehicle can only wait on the sidewalk outside the parking lot gate. Once the car is opened, the first car on the sidewalk will enter the parking lot. If a car wants to leave in the parking lot, after he enters the parking lot, the car must exit the parking lot to make way for it. After the parking lot is opened, the vehicles will enter the original order.)