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1#
2# Eight Queens in Tcl
3#
4# by Karl Lehenbauer, 23 Nov 1990
5#
6#-----------------------------------------------------------------------------
7# $Id: 8queens.tcl,v 2.0 1992/10/16 04:51:36 markd Rel $
8#-----------------------------------------------------------------------------
9#
10proc none_attacking {rank position} {
11 global queens
12 loop i 1 $rank {
13 set j $queens([expr {$rank - $i}])
14 if {($j==$position-$i) || ($j==$position) || ($j==$position+$i)} {
15 return 0
16 }
17 }
18 return 1
19}
20
21proc solution {} {
22 global queens
23 echo $queens(1) $queens(2) $queens(3) $queens(4) $queens(5) $queens(6) $queens(7) $queens(8)
24}
25
26proc x8queens {rank} {
27 global queens
28 set queens($rank) 1
29 loop i 1 9 {
30 if [none_attacking $rank $i] {
31 set queens($rank) $i
32 if {$rank != 8} {
33 x8queens [expr $rank+1]
34 } else {
35 solution
36 return
37 }
38 }
39 }
40}
41
42proc 8queens {} {
43 x8queens 1
44}
45
46global interactiveSession
47if !$interactiveSession 8queens
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