1 # Copyright (C) 2008 Pat Thoyts <patthoyts@users.sourceforge.net>
3 # Calculate a Knight's tour of a chessboard.
5 # This uses Warnsdorff's rule to calculate the next square each
6 # time. This specifies that the next square should be the one that
7 # has the least number of available moves.
9 # Using this rule it is possible to get to a position where
10 # there are no squares available to move into. In this implementation
11 # this occurs when the starting square is d6.
13 # To solve this fault an enhancement to the rule is that if we
14 # have a choice of squares with an equal score, we should choose
15 # the one nearest the edge of the board.
17 # If the call to the Edgemost function is commented out you can see
20 # You can drag the knight to a specific square to start if you wish.
21 # If you let it repeat then it will choose random start positions
24 package require Tk 8.5
26 # Return a list of accessible squares from a given square
27 proc ValidMoves {square} {
29 foreach pair {{-1 -2} {-2 -1} {-2 1} {-1 2} {1 2} {2 1} {2 -1} {1 -2}} {
30 set col [expr {($square % 8) + [lindex $pair 0]}]
31 set row [expr {($square / 8) + [lindex $pair 1]}]
32 if {$row > -1 && $row < 8 && $col > -1 && $col < 8} {
33 lappend moves [expr {$row * 8 + $col}]
39 # Return the number of available moves for this square
40 proc CheckSquare {square} {
43 foreach test [ValidMoves $square] {
44 if {[lsearch -exact -integer $visited $test] == -1} {
51 # Select the next square to move to. Returns -1 if there are no available
52 # squares remaining that we can move to.
57 foreach testSquare [ValidMoves $square] {
58 if {[lsearch -exact -integer $visited $testSquare] == -1} {
59 set count [CheckSquare $testSquare]
60 if {$count < $minimum} {
62 set nextSquare $testSquare
63 } elseif {$count == $minimum} {
64 # to remove the enhancement to Warnsdorff's rule
65 # remove the next line:
66 set nextSquare [Edgemost $nextSquare $testSquare]
73 # Select the square nearest the edge of the board
75 set colA [expr {3-int(abs(3.5-($a%8)))}]
76 set colB [expr {3-int(abs(3.5-($b%8)))}]
77 set rowA [expr {3-int(abs(3.5-($a/8)))}]
78 set rowB [expr {3-int(abs(3.5-($b/8)))}]
79 return [expr {($colA * $rowA) < ($colB * $rowB) ? $a : $b}]
82 # Display a square number as a standard chess square notation.
84 return [format %c%d [expr {97 + $square % 8}] \
85 [expr {$square / 8 + 1}]]
88 # Perform a Knight's move and schedule the next move.
89 proc MovePiece {dlg last square} {
93 $dlg.f.txt insert end "[llength $visited]. [N $last] .. [N $square]\n" {}
95 $dlg.f.c itemconfigure [expr {1+$last}] -state normal -outline black
96 $dlg.f.c itemconfigure [expr {1+$square}] -state normal -outline red
97 $dlg.f.c moveto knight {*}[lrange [$dlg.f.c coords [expr {1+$square}]] 0 1]
98 lappend visited $square
99 set next [Next $square]
101 variable aid [after $delay [list MovePiece $dlg $square $next]]
103 $dlg.tf.b1 configure -state normal
104 if {[llength $visited] == 64} {
106 if {$initial == $square} {
107 $dlg.f.txt insert end "Closed tour!"
109 $dlg.f.txt insert end "Success\n" {}
111 after [expr {$delay * 2}] [namespace code \
112 [list Tour $dlg [expr {int(rand() * 64)}]]]
116 $dlg.f.txt insert end "FAILED!\n" {}
121 # Begin a new tour of the board given a random start position
122 proc Tour {dlg {square {}}} {
124 $dlg.f.txt delete 1.0 end
125 $dlg.tf.b1 configure -state disabled
126 for {set n 0} {$n < 64} {incr n} {
127 $dlg.f.c itemconfigure $n -state disabled -outline black
130 set coords [lrange [$dlg.f.c coords knight] 0 1]
131 set square [expr {[$dlg.f.c find closest {*}$coords 0 65]-1}]
133 variable initial $square
134 after idle [list MovePiece $dlg $initial $initial]
139 catch {after cancel $aid}
147 proc SetDelay {new} {
148 variable delay [expr {int($new)}]
151 proc DragStart {w x y} {
153 $w addtag selected withtag current
154 variable dragging [list $x $y]
156 proc DragMotion {w x y} {
158 if {[info exists dragging]} {
159 $w move selected [expr {$x - [lindex $dragging 0]}] \
160 [expr {$y - [lindex $dragging 1]}]
161 variable dragging [list $x $y]
164 proc DragEnd {w x y} {
165 set square [$w find closest $x $y 0 65]
166 $w moveto selected {*}[lrange [$w coords $square] 0 1]
168 variable dragging ; unset dragging
172 catch {destroy .knightstour}
173 set dlg [toplevel .knightstour]
174 wm title $dlg "Knights tour"
176 set f [ttk::frame $dlg.f]
177 set c [canvas $f.c -width 240 -height 240]
178 text $f.txt -width 10 -height 1 -background white \
179 -yscrollcommand [list $f.vs set] -font {Arial 8}
180 ttk::scrollbar $f.vs -command [list $f.txt yview]
183 variable continuous 0
185 ttk::label $dlg.tf.ls -text Speed
186 ttk::scale $dlg.tf.sc -from 8 -to 2000 -command [list SetDelay] \
187 -variable [namespace which -variable delay]
188 ttk::checkbutton $dlg.tf.cc -text Repeat \
189 -variable [namespace which -variable continuous]
190 ttk::button $dlg.tf.b1 -text Start -command [list Tour $dlg]
191 ttk::button $dlg.tf.b2 -text Exit -command [list Exit $dlg]
193 for {set row 7} {$row != -1} {incr row -1} {
194 for {set col 0} {$col < 8} {incr col} {
195 if {(($col & 1) ^ ($row & 1))} {
196 set fill tan3 ; set dfill tan4
198 set fill bisque ; set dfill bisque3
200 set coords [list [expr {$col * 30 + 4}] [expr {$row * 30 + 4}] \
201 [expr {$col * 30 + 30}] [expr {$row * 30 + 30}]]
202 $c create rectangle $coords -fill $fill -disabledfill $dfill \
203 -width 2 -state disabled
206 if {[tk windowingsystem] ne "x11"} {
207 catch {eval font create KnightFont -size -24}
208 $c create text 0 0 -font KnightFont -text "\u265e" \
209 -anchor nw -tags knight -fill black -activefill "#600000"
211 # On X11 we cannot reliably tell if the \u265e glyph is available
212 # so just use a polygon
214 2 25 24 25 21 19 20 8 14 0 10 0 0 13 0 16
215 2 17 4 14 5 15 3 17 5 17 9 14 10 15 5 21
217 $c create polygon $pts -tag knight -offset 8 \
218 -fill black -activefill "#600000"
220 $c moveto knight {*}[lrange [$c coords [expr {1 + int(rand() * 64)}]] 0 1]
221 $c bind knight <ButtonPress-1> [namespace code [list DragStart %W %x %y]]
222 $c bind knight <Motion> [namespace code [list DragMotion %W %x %y]]
223 $c bind knight <ButtonRelease-1> [namespace code [list DragEnd %W %x %y]]
225 grid $c $f.txt $f.vs -sticky news
226 grid rowconfigure $f 0 -weight 1
227 grid columnconfigure $f 1 -weight 1
229 grid $f - - - - - -sticky news
230 set things [list $dlg.tf.ls $dlg.tf.sc $dlg.tf.cc $dlg.tf.b1]
231 if {![info exists ::widgetDemo]} {
232 lappend things $dlg.tf.b2
233 if {[tk windowingsystem] ne "aqua"} {
234 set things [linsert $things 0 [ttk::sizegrip $dlg.tf.sg]]
237 pack {*}$things -side right
238 if {[tk windowingsystem] eq "aqua"} {
239 pack configure {*}$things -padx {4 4} -pady {12 12}
240 pack configure [lindex $things 0] -padx {4 24}
241 pack configure [lindex $things end] -padx {16 4}
243 grid $dlg.tf - - - - - -sticky ew
244 if {[info exists ::widgetDemo]} {
245 grid [addSeeDismiss $dlg.buttons $dlg] - - - - - -sticky ew
248 grid rowconfigure $dlg 0 -weight 1
249 grid columnconfigure $dlg 0 -weight 1
251 bind $dlg <Control-F2> {console show}
252 bind $dlg <Return> [list $dlg.tf.b1 invoke]
253 bind $dlg <Escape> [list $dlg.tf.b2 invoke]
254 bind $dlg <Destroy> [namespace code [list Stop]]
255 wm protocol $dlg WM_DELETE_WINDOW [namespace code [list Exit $dlg]]
261 if {![winfo exists .knightstour]} {
262 if {![info exists widgetDemo]} { wm withdraw . }
263 set r [catch [linsert $argv 0 CreateGUI] err]
265 tk_messageBox -icon error -title "Error" -message $err
267 if {![info exists widgetDemo]} { exit $r }