Canterbury Puzzle 13 · Monk’s Garden 13

The Sergeant of the Law was "full rich of excellence. Discreet he was, and of great reverence." He was a very busy man, but, like many of us to-day, "he seemed busier than he was." He was talking one evening of prisons and prisoners, and at length made the following remarks: "And that which I have been saying doth forsooth call to my mind that this morn I bethought me of a riddle that I will now put forth." He then produced a slip of vellum, on which was drawn the curious plan that is now given. "Here," saith he, "be nine dungeons, with a prisoner in every dungeon save one, which is empty. These prisoners be numbered in order, 7, 5, 6, 8, 2, 1, 4, 3, and I desire to know how they can, in as few moves as possible, put themselves in the order 1, 2, 3, 4, 5, 6, 7, 8. One prisoner may move at a time along the passage to the dungeon that doth happen to be empty, but never, on pain of death, may two men be in any dungeon at the same time. How may it be done?" If the reader makes a rough plan on a sheet of paper and uses numbered counters, he will find it an interesting pastime to arrange the prisoners in the fewest possible moves. As there is never more than one vacant dungeon at a time to be moved into, the moves may be recorded in this simple way: 3—2—1—6, and so on.

这位法律中士“充满了卓越的才能。他很谨慎，而且非常受人尊敬”。他是一个非常忙碌的人，但是，就像我们今天的许多人一样，“他看起来比实际上更忙。”一天晚上，他正在谈论监狱和囚犯，最后发表了以下言论：“我刚才所说的确实让我想起今天早上我想到了一个谜语，现在我将提出这个谜语。”然后他拿出一张牛皮纸，上面画着现在给出的奇怪计划。 “这里，”他说，“有九个地牢，每个地牢里都有一名囚犯，只有一个是空的。这些囚犯按顺序编号：7、5、6、8、2、1、4、3，我想知道他们如何以尽可能少的移动次数将自己排列成 1、2、3、4、5、6、7、8 的顺序。一名囚犯可以移动在通往地牢的通道上，碰巧是空的，但绝对不能有两个人同时在任何地牢里，违者处死。”如果读者在一张纸上制定一个粗略的计划并使用编号计数器，他会发现以尽可能少的步数安排囚犯是一种有趣的消遣。由于每次移动的空地牢不会超过一个，因此移动可以用这种简单的方式记录：3-2-1-6，依此类推。