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Diffstat (limited to 'lisp/play/hanoi.el')
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diff --git a/lisp/play/hanoi.el b/lisp/play/hanoi.el index e65608235fd..99e2acdd92a 100644 --- a/lisp/play/hanoi.el +++ b/lisp/play/hanoi.el @@ -8,6 +8,35 @@ ; This is in the public domain ; since he distributed it without copyright notice in 1985. +;;; Commentary: + +;; Solves the Towers of Hanoi puzzle while-U-wait. +;; +;; The puzzle: Start with N rings, decreasing in sizes from bottom to +;; top, stacked around a post. There are two other posts. Your mission, +;; should you choose to accept it, is to shift the pile, stacked in its +;; original order, to another post. +;; +;; The challenge is to do it in the fewest possible moves. Each move +;; shifts one ring to a different post. But there's a rule; you can +;; only stack a ring on top of a larger one. +;; +;; The simplest nontrivial version of this puzzle is N = 3. Solution +;; time rises as 2**N, and programs to solve it have long been considered +;; classic introductory exercises in the use of recursion. +;; +;; The puzzle is called `Towers of Hanoi' because an early popular +;; presentation wove a fanciful legend around it. According to this +;; myth (uttered long before the Vietnam War), there is a Buddhist +;; monastery at Hanoi which contains a large room with three time-worn +;; posts in it surrounded by 21 golden discs. Monks, acting out the +;; command of an ancient prophecy, have been moving these disks, in +;; accordance with the rules of the puzzle, once every day since the +;; monastery was founded over a thousand years ago. They are said +;; believe that when the last move of the puzzle is completed, the +;; world will end in a clap of thunder. Fortunately, they are nowhere +;; even close to being done... + ;;; Code: ;;; |