1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
|
;;; hanoi.el --- towers of hanoi in GNUmacs
;; Author: Damon Anton Permezel
;; Maintainer: FSF
;; Keywords: games
; Author (a) 1985, Damon Anton Permezel
; 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:
;;;
;;; hanoi-topos - direct cursor addressing
;;;
(defun hanoi-topos (row col)
(goto-line row)
(beginning-of-line)
(forward-char col))
;;;
;;; hanoi - user callable Towers of Hanoi
;;;
;;;###autoload
(defun hanoi (nrings)
"Towers of Hanoi diversion. Argument is number of rings."
(interactive "p")
(if (<= nrings 1) (setq nrings 7))
(let* (floor-row
fly-row
(window-height (1- (window-height (selected-window))))
(window-width (window-width (selected-window)))
;; This is half the spacing to use between poles.
(pole-spacing (/ window-width 6)))
(if (not (and (> window-height (1+ nrings))
(> pole-spacing nrings)))
(progn
(delete-other-windows)
(if (not (and (> (setq window-height
(1- (window-height (selected-window))))
(1+ nrings))
(> (setq pole-spacing (/ window-width 6))
nrings)))
(error "Window is too small (need at least %dx%d)"
(* 6 (1+ nrings)) (+ 2 nrings)))))
(setq floor-row (if (> (- window-height 3) (1+ nrings))
(- window-height 3) window-height))
(let ((fly-row (- floor-row nrings 1))
;; pole: column . fill height
(pole-1 (cons (1- pole-spacing) floor-row))
(pole-2 (cons (1- (* 3 pole-spacing)) floor-row))
(pole-3 (cons (1- (* 5 pole-spacing)) floor-row))
(rings (make-vector nrings nil)))
;; construct the ring list
(let ((i 0))
(while (< i nrings)
;; ring: [pole-number string empty-string]
(aset rings i (vector nil
(make-string (+ i i 3) (+ ?0 (% i 10)))
(make-string (+ i i 3) ?\ )))
(setq i (1+ i))))
;;
;; init the screen
;;
(switch-to-buffer "*Hanoi*")
(setq buffer-read-only nil)
(buffer-disable-undo (current-buffer))
(erase-buffer)
(let ((i 0))
(while (< i floor-row)
(setq i (1+ i))
(insert-char ?\ (1- window-width))
(insert ?\n)))
(insert-char ?= (1- window-width))
(let ((n 1))
(while (< n 6)
(hanoi-topos fly-row (1- (* n pole-spacing)))
(setq n (+ n 2))
(let ((i fly-row))
(while (< i floor-row)
(setq i (1+ i))
(next-line 1)
(insert ?\|)
(delete-char 1)
(backward-char 1)))))
;(sit-for 0)
;;
;; now draw the rings in their initial positions
;;
(let ((i 0)
ring)
(while (< i nrings)
(setq ring (aref rings (- nrings 1 i)))
(aset ring 0 (- floor-row i))
(hanoi-topos (cdr pole-1)
(- (car pole-1) (- nrings i)))
(hanoi-draw-ring ring t nil)
(setcdr pole-1 (1- (cdr pole-1)))
(setq i (1+ i))))
(setq buffer-read-only t)
(sit-for 0)
;; Disable display of line and column numbers, for speed.
(let ((line-number-mode nil)
(column-number-mode nil))
;; do it!
(hanoi0 (1- nrings) pole-1 pole-2 pole-3))
(goto-char (point-min))
(message "Done")
(setq buffer-read-only t)
(force-mode-line-update)
(sit-for 0))))
;;;
;;; hanoi0 - work horse of hanoi
;;;
(defun hanoi0 (n from to work)
(cond ((input-pending-p)
(signal 'quit (list "I can tell you've had enough")))
((< n 0))
(t
(hanoi0 (1- n) from work to)
(hanoi-move-ring n from to)
(hanoi0 (1- n) work to from))))
;;;
;;; hanoi-move-ring - move ring 'n' from 'from' to 'to'
;;;
;;;
(defun hanoi-move-ring (n from to)
(let ((ring (aref rings n)) ; ring <- ring: (ring# . row)
(buffer-read-only nil))
(let ((row (aref ring 0)) ; row <- row ring is on
(col (- (car from) n 1)) ; col <- left edge of ring
(dst-col (- (car to) n 1)) ; dst-col <- dest col for left edge
(dst-row (cdr to))) ; dst-row <- dest row for ring
(hanoi-topos row col)
(while (> row fly-row) ; move up to the fly row
(hanoi-draw-ring ring nil t) ; blank out ring
(previous-line 1) ; move up a line
(hanoi-draw-ring ring t nil) ; redraw
(sit-for 0)
(setq row (1- row)))
(setcdr from (1+ (cdr from))) ; adjust top row
;;
;; fly the ring over to the right pole
;;
(while (not (equal dst-col col))
(cond ((> dst-col col) ; dst-col > col: right shift
(end-of-line 1)
(delete-backward-char 2)
(beginning-of-line 1)
(insert ?\ ?\ )
(sit-for 0)
(setq col (1+ (1+ col))))
((< dst-col col) ; dst-col < col: left shift
(beginning-of-line 1)
(delete-char 2)
(end-of-line 1)
(insert ?\ ?\ )
(sit-for 0)
(setq col (1- (1- col))))))
;;
;; let the ring float down
;;
(hanoi-topos fly-row dst-col)
(while (< row dst-row) ; move down to the dest row
(hanoi-draw-ring ring nil (> row fly-row)) ; blank out ring
(next-line 1) ; move down a line
(hanoi-draw-ring ring t nil) ; redraw ring
(sit-for 0)
(setq row (1+ row)))
(aset ring 0 dst-row)
(setcdr to (1- (cdr to)))))) ; adjust top row
;;;
;;; draw-ring - draw the ring at point, leave point unchanged
;;;
;;; Input:
;;; ring
;;; f1 - flag: t -> draw, nil -> erase
;;; f2 - flag: t -> erasing and need to draw ?\|
;;;
(defun hanoi-draw-ring (ring f1 f2)
(save-excursion
(let* ((string (if f1 (aref ring 1) (aref ring 2)))
(len (length string)))
(delete-char len)
(insert string)
(if f2
(progn
(backward-char (/ (+ len 1) 2))
(delete-char 1) (insert ?\|))))))
(provide 'hanoi)
;;; hanoi.el ends here
|
