Now, as obvious a statement as that is in this algorithm, it turns out that is the key to this whole problem being solved correctly without my algorithm looping infinitely.

这是此算法中很明显的一句话，也是正确解决,整个问题的关键,否则此算法就会陷入死循环。

哈佛公开课 - 计算机科学课程节选