十字路*通灯，南北向为主干道，东西向为支道，每个道口安装一组交通灯：红、黄、绿。设计十字路口的交通灯控制器，使交通灯按状态1 状态2 状态3 状态4 的规律变化，循环不止。

状态1：东西向绿灯亮，南北向红灯亮，其他灯全灭，保持30 秒

状态2：东西向黄灯亮，南北向红灯亮，其他灯全灭，保持5 秒

状态3：东西向红灯亮，南北向绿灯亮，其他灯全灭，保持20 秒

状态4：东西向红灯亮，南北向黄灯亮，其他灯全灭，保持5 秒-Crossroads of traffic lights, the north-south trunk road, the east-west road to support each crossing to install a set of traffic lights: red, yellow, green. Design crossroads traffic light controller, so that the traffic lights by the state 1 state 2 state 3 4 state law changes, circulation more than. State 1: things to green light, red light from north to south, the other lights all off, 30 seconds Status 2: something to yellow light, red light from north to south, the other lights all off, 5 seconds state 3: the red stuff light, green light from north to south, the other lights all off, 20 seconds Status 4: something to the red light, yellow light from north to south, the other lights all off, 5 seconds