设计一个秒表，该跑表使用一个按钮k工作，当第1次按下按钮时，秒表开始计数，第2次按下按钮时，秒表停止计数，第3次按下按钮时，秒表计数器继续计数，第4次按下按钮时，秒表计数器停止计数，如此反复。若是在停止计数状态，按钮的按下时间超出2s，则秒表计数器清零-Design a stopwatch, the stopwatch with a button k work, when the 1st button is pressed, the stopwatch starts counting, press the button 2 times, the stopwatch stops counting, 3rd button is pressed, the stopwatch counter continues to count , 4 times the button is pressed, the stopwatch counter stops counting, and so forth. If the state stopped counting, pressing the button longer than 2s, the stopwatch counter is cleared