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1a06eabd ER |
1 | ;;; hanoi.el --- towers of hanoi in GNUmacs |
2 | ||
fc68affa ER |
3 | ;; Author: Damon Anton Permezel |
4 | ;; Maintainer: FSF | |
fc68affa ER |
5 | ;; Keywords: games |
6 | ||
80a677d9 | 7 | ; Author (a) 1985, Damon Anton Permezel |
2f4b997c RS |
8 | ; This is in the public domain |
9 | ; since he distributed it without copyright notice in 1985. | |
80a677d9 | 10 | |
e41b2db1 ER |
11 | ;;; Commentary: |
12 | ||
13 | ;; Solves the Towers of Hanoi puzzle while-U-wait. | |
14 | ;; | |
15 | ;; The puzzle: Start with N rings, decreasing in sizes from bottom to | |
16 | ;; top, stacked around a post. There are two other posts. Your mission, | |
17 | ;; should you choose to accept it, is to shift the pile, stacked in its | |
18 | ;; original order, to another post. | |
19 | ;; | |
20 | ;; The challenge is to do it in the fewest possible moves. Each move | |
21 | ;; shifts one ring to a different post. But there's a rule; you can | |
22 | ;; only stack a ring on top of a larger one. | |
23 | ;; | |
24 | ;; The simplest nontrivial version of this puzzle is N = 3. Solution | |
25 | ;; time rises as 2**N, and programs to solve it have long been considered | |
26 | ;; classic introductory exercises in the use of recursion. | |
27 | ;; | |
28 | ;; The puzzle is called `Towers of Hanoi' because an early popular | |
29 | ;; presentation wove a fanciful legend around it. According to this | |
30 | ;; myth (uttered long before the Vietnam War), there is a Buddhist | |
31 | ;; monastery at Hanoi which contains a large room with three time-worn | |
32 | ;; posts in it surrounded by 21 golden discs. Monks, acting out the | |
33 | ;; command of an ancient prophecy, have been moving these disks, in | |
34 | ;; accordance with the rules of the puzzle, once every day since the | |
35 | ;; monastery was founded over a thousand years ago. They are said | |
36 | ;; believe that when the last move of the puzzle is completed, the | |
37 | ;; world will end in a clap of thunder. Fortunately, they are nowhere | |
38 | ;; even close to being done... | |
39 | ||
fc68affa ER |
40 | ;;; Code: |
41 | ||
80a677d9 JA |
42 | ;;; |
43 | ;;; hanoi-topos - direct cursor addressing | |
44 | ;;; | |
45 | (defun hanoi-topos (row col) | |
46 | (goto-line row) | |
47 | (beginning-of-line) | |
48 | (forward-char col)) | |
49 | ||
50 | ;;; | |
51 | ;;; hanoi - user callable Towers of Hanoi | |
52 | ;;; | |
f9f9507e | 53 | ;;;###autoload |
80a677d9 JA |
54 | (defun hanoi (nrings) |
55 | "Towers of Hanoi diversion. Argument is number of rings." | |
f5bb8a9e KH |
56 | (interactive "p") |
57 | (if (<= nrings 1) (setq nrings 7)) | |
84df0b37 JB |
58 | (let* (floor-row |
59 | fly-row | |
f5bb8a9e | 60 | (window-height (1- (window-height (selected-window)))) |
84df0b37 JB |
61 | (window-width (window-width (selected-window))) |
62 | ||
f5bb8a9e KH |
63 | ;; This is half the spacing to use between poles. |
64 | (pole-spacing (/ window-width 6))) | |
65 | (if (not (and (> window-height (1+ nrings)) | |
66 | (> pole-spacing nrings))) | |
67 | (progn | |
68 | (delete-other-windows) | |
69 | (if (not (and (> (setq window-height | |
70 | (1- (window-height (selected-window)))) | |
71 | (1+ nrings)) | |
72 | (> (setq pole-spacing (/ window-width 6)) | |
73 | nrings))) | |
74 | (error "Window is too small (need at least %dx%d)" | |
75 | (* 6 (1+ nrings)) (+ 2 nrings))))) | |
76 | (setq floor-row (if (> (- window-height 3) (1+ nrings)) | |
77 | (- window-height 3) window-height)) | |
80a677d9 JA |
78 | (let ((fly-row (- floor-row nrings 1)) |
79 | ;; pole: column . fill height | |
f5bb8a9e KH |
80 | (pole-1 (cons (1- pole-spacing) floor-row)) |
81 | (pole-2 (cons (1- (* 3 pole-spacing)) floor-row)) | |
82 | (pole-3 (cons (1- (* 5 pole-spacing)) floor-row)) | |
80a677d9 JA |
83 | (rings (make-vector nrings nil))) |
84 | ;; construct the ring list | |
85 | (let ((i 0)) | |
86 | (while (< i nrings) | |
87 | ;; ring: [pole-number string empty-string] | |
88 | (aset rings i (vector nil | |
f5bb8a9e | 89 | (make-string (+ i i 3) (+ ?0 (% i 10))) |
80a677d9 JA |
90 | (make-string (+ i i 3) ?\ ))) |
91 | (setq i (1+ i)))) | |
92 | ;; | |
93 | ;; init the screen | |
94 | ;; | |
95 | (switch-to-buffer "*Hanoi*") | |
96 | (setq buffer-read-only nil) | |
97 | (buffer-disable-undo (current-buffer)) | |
98 | (erase-buffer) | |
99 | (let ((i 0)) | |
100 | (while (< i floor-row) | |
101 | (setq i (1+ i)) | |
102 | (insert-char ?\ (1- window-width)) | |
103 | (insert ?\n))) | |
104 | (insert-char ?= (1- window-width)) | |
105 | ||
106 | (let ((n 1)) | |
107 | (while (< n 6) | |
f5bb8a9e | 108 | (hanoi-topos fly-row (1- (* n pole-spacing))) |
80a677d9 JA |
109 | (setq n (+ n 2)) |
110 | (let ((i fly-row)) | |
111 | (while (< i floor-row) | |
112 | (setq i (1+ i)) | |
113 | (next-line 1) | |
114 | (insert ?\|) | |
115 | (delete-char 1) | |
116 | (backward-char 1))))) | |
117 | ;(sit-for 0) | |
118 | ;; | |
119 | ;; now draw the rings in their initial positions | |
120 | ;; | |
121 | (let ((i 0) | |
122 | ring) | |
123 | (while (< i nrings) | |
124 | (setq ring (aref rings (- nrings 1 i))) | |
125 | (aset ring 0 (- floor-row i)) | |
126 | (hanoi-topos (cdr pole-1) | |
127 | (- (car pole-1) (- nrings i))) | |
128 | (hanoi-draw-ring ring t nil) | |
129 | (setcdr pole-1 (1- (cdr pole-1))) | |
130 | (setq i (1+ i)))) | |
131 | (setq buffer-read-only t) | |
132 | (sit-for 0) | |
09d13f4c KH |
133 | ;; Disable display of line and column numbers, for speed. |
134 | (let ((line-number-mode nil) | |
135 | (column-number-mode nil)) | |
136 | ;; do it! | |
137 | (hanoi0 (1- nrings) pole-1 pole-2 pole-3)) | |
80a677d9 JA |
138 | (goto-char (point-min)) |
139 | (message "Done") | |
140 | (setq buffer-read-only t) | |
433c31eb | 141 | (force-mode-line-update) |
80a677d9 JA |
142 | (sit-for 0)))) |
143 | ||
144 | ;;; | |
145 | ;;; hanoi0 - work horse of hanoi | |
146 | ;;; | |
147 | (defun hanoi0 (n from to work) | |
148 | (cond ((input-pending-p) | |
149 | (signal 'quit (list "I can tell you've had enough"))) | |
150 | ((< n 0)) | |
151 | (t | |
152 | (hanoi0 (1- n) from work to) | |
153 | (hanoi-move-ring n from to) | |
154 | (hanoi0 (1- n) work to from)))) | |
155 | ||
156 | ;;; | |
157 | ;;; hanoi-move-ring - move ring 'n' from 'from' to 'to' | |
158 | ;;; | |
159 | ;;; | |
160 | (defun hanoi-move-ring (n from to) | |
161 | (let ((ring (aref rings n)) ; ring <- ring: (ring# . row) | |
162 | (buffer-read-only nil)) | |
163 | (let ((row (aref ring 0)) ; row <- row ring is on | |
164 | (col (- (car from) n 1)) ; col <- left edge of ring | |
165 | (dst-col (- (car to) n 1)) ; dst-col <- dest col for left edge | |
166 | (dst-row (cdr to))) ; dst-row <- dest row for ring | |
167 | (hanoi-topos row col) | |
168 | (while (> row fly-row) ; move up to the fly row | |
169 | (hanoi-draw-ring ring nil t) ; blank out ring | |
170 | (previous-line 1) ; move up a line | |
171 | (hanoi-draw-ring ring t nil) ; redraw | |
172 | (sit-for 0) | |
173 | (setq row (1- row))) | |
174 | (setcdr from (1+ (cdr from))) ; adjust top row | |
175 | ;; | |
176 | ;; fly the ring over to the right pole | |
177 | ;; | |
178 | (while (not (equal dst-col col)) | |
179 | (cond ((> dst-col col) ; dst-col > col: right shift | |
180 | (end-of-line 1) | |
181 | (delete-backward-char 2) | |
182 | (beginning-of-line 1) | |
183 | (insert ?\ ?\ ) | |
184 | (sit-for 0) | |
185 | (setq col (1+ (1+ col)))) | |
186 | ((< dst-col col) ; dst-col < col: left shift | |
187 | (beginning-of-line 1) | |
188 | (delete-char 2) | |
189 | (end-of-line 1) | |
190 | (insert ?\ ?\ ) | |
191 | (sit-for 0) | |
192 | (setq col (1- (1- col)))))) | |
193 | ;; | |
194 | ;; let the ring float down | |
195 | ;; | |
196 | (hanoi-topos fly-row dst-col) | |
197 | (while (< row dst-row) ; move down to the dest row | |
198 | (hanoi-draw-ring ring nil (> row fly-row)) ; blank out ring | |
199 | (next-line 1) ; move down a line | |
200 | (hanoi-draw-ring ring t nil) ; redraw ring | |
201 | (sit-for 0) | |
202 | (setq row (1+ row))) | |
203 | (aset ring 0 dst-row) | |
204 | (setcdr to (1- (cdr to)))))) ; adjust top row | |
205 | ||
206 | ;;; | |
207 | ;;; draw-ring - draw the ring at point, leave point unchanged | |
208 | ;;; | |
209 | ;;; Input: | |
210 | ;;; ring | |
211 | ;;; f1 - flag: t -> draw, nil -> erase | |
212 | ;;; f2 - flag: t -> erasing and need to draw ?\| | |
213 | ;;; | |
214 | (defun hanoi-draw-ring (ring f1 f2) | |
215 | (save-excursion | |
216 | (let* ((string (if f1 (aref ring 1) (aref ring 2))) | |
217 | (len (length string))) | |
218 | (delete-char len) | |
219 | (insert string) | |
220 | (if f2 | |
221 | (progn | |
222 | (backward-char (/ (+ len 1) 2)) | |
223 | (delete-char 1) (insert ?\|)))))) | |
224 | ||
62daf326 RM |
225 | (provide 'hanoi) |
226 | ||
227 | ;;; hanoi.el ends here |