That's the finger thing from left finger to right finger going back and forth across the board, never touching a number more than once.
在合并时,我的左手手指,和右手手指来回地在黑板上移动,但对每个数字只会碰到一次。
哈佛公开课 - 计算机科学课程节选
应用推荐
模块上移
模块下移
不移动