可以使用c51，实现交通灯的设计，可以有十字路口，十字路口有红、绿、黄，三种灯，在不同的情况下，应该亮什么灯(C51 can be used to achieve traffic lights design, you can have a crossroads, the intersection has red, green, yellow, three kinds of lights, in different circumstances, what should light)