8 Queens in Smalltalk

 1 Object subclass: #Queen
 2     instanceVariableNames: ‘position‘
 3     classVariableNames: ‘‘
 4     poolDictionaries: ‘‘
 5     category: ‘Queens‘!
 6 !Queen commentStamp: ‘TomZhao 10/15/2015 13:17‘ prior: 0!
 7 Queen at: 1@1.!
 8 
 9 
10 !Queen methodsFor: ‘accessing‘ stamp: ‘TomZhao 10/15/2015 13:22‘!
11 moveTo: aPoint 
12     self position: aPoint.! !
13 
14 !Queen methodsFor: ‘accessing‘ stamp: ‘TomZhao 10/15/2015 13:41‘!
15 position
16     ^ position! !
17 
18 !Queen methodsFor: ‘accessing‘ stamp: ‘TomZhao 10/15/2015 13:17‘!
19 position: aPoint 
20     position := aPoint! !
21 
22 
23 !Queen methodsFor: ‘as yet unclassified‘ stamp: ‘TomZhao 10/15/2015 13:29‘!
24 meets: queen
25     |a b|
26     a := self position.
27     b := queen position.
28     ^(a x = b x) | (a y = b y) | ((a x - b x) abs = (a y - b y) abs).! !
29 
30 
31 !Queen methodsFor: ‘testing‘ stamp: ‘TomZhao 10/15/2015 13:39‘!
32 isSafeWith: queens
33     ^queens allSatisfy: [ :queen | (self meets: queen) not ].! !
34 
35 "-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- "!
36 
37 Queen class
38     instanceVariableNames: ‘‘!
39 
40 !Queen class methodsFor: ‘as yet unclassified‘ stamp: ‘TomZhao 10/15/2015 09:42‘!
41 at: aPoint
42     "comment stating purpose of message"
43     | tmp |
44     tmp := self new.
45     tmp position: aPoint.
46     ^tmp.! !
47 
48 
49 Object subclass: #Queens
50     instanceVariableNames: ‘size‘
51     classVariableNames: ‘‘
52     poolDictionaries: ‘‘
53     category: ‘Queens‘!
54 !Queens commentStamp: ‘TomZhao 10/15/2015 14:25‘ prior: 0!
55 Queens run: 6.!
56 
57 
58 !Queens methodsFor: ‘acccessing‘ stamp: ‘TomZhao 10/15/2015 13:21‘!
59 size: anInteger 
60     size := anInteger! !
61 
62 
63 !Queens methodsFor: ‘as yet unclassified‘ stamp: ‘TomZhao 10/15/2015 14:39‘!
64 printSolution: queens
65     Transcript show: ($- join: (queens collect: [ :q | q position y ])); cr.! !
66 
67 
68 !Queens methodsFor: ‘running‘ stamp: ‘TomZhao 10/15/2015 14:53‘!
69 run: anInteger 
70     self size: anInteger.
71     self solve: 1 with: OrderedCollection new.
72     Transcript show: ‘Game Over!!‘; cr.
73     ^self.! !
74 
75 !Queens methodsFor: ‘running‘ stamp: ‘TomZhao 10/15/2015 14:52‘!
76 solve: nRow with: queens 
77     | q tmp |
78     q :=Queen at: nRow@1.
79     (1 to: size) do:  [ :col |
80         q moveTo: nRow@col.
81         tmp := queens copy.
82         (q isSafeWith: tmp)
83             ifTrue: [
84                 tmp add: q.
85                 nRow = size
86                     ifTrue:[self printSolution: tmp. ]
87                     ifFalse:[self solve: (nRow+1) with: tmp.]]].! !
88 
89 "-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- "!
90 
91 Queens class
92     instanceVariableNames: ‘‘!
93 
94 !Queens class methodsFor: ‘as yet unclassified‘ stamp: ‘TomZhao 10/13/2015 17:01‘!
95 run: size
96      
97     Queens new 
98             run: size.
99     ^self.! !