aparler/RosettaCodeData
1
0
Fork 0
Code Issues 12 Pull requests 3 Projects Releases Packages Wiki Activity Actions

Initial data commit

Browse source
This commit is contained in:
Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 72d218235f
commit f23f22d71c
199087 changed files with 3378941 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

50
Task/N-queens-problem/REXX/n-queens-problem.rexx Normal file
View file

@ -0,0 +1,50 @@
/*REXX program places N queens on an NxN chessboard (the eight queens problem). */
parse arg N . /*obtain optional argument from the CL.*/
if N=='' | N=="," then N= 8 /*Not specified: Then use the default.*/
if N<1 then call nOK /*display a message, the board is bad. */
rank= 1; file= 1; #= 0 /*starting rank&file; #≡number queens.*/
@.= 0; pad= left('', 9* (N<18) ) /*define empty board; set indentation.*/
/* [↓] rank&file ≡ chessboard row&cols*/
do while #<N; @.file.rank= 1 /*keep placing queens until we're done.*/
if ok(file, rank) then do; file= 1; #= #+1 /*Queen not being attacked? Then eureka*/
rank= rank+1 /*use another attempt at another rank. */
iterate /*go and try another queen placement. */
end /* [↑] found a good queen placement. */
@.file.rank= 0 /*It isn't safe. So remove this queen.*/
file= file + 1 /*So, try the next (higher) chess file.*/
do while file>N; rank= rank - 1; if rank==0 then call nOK
do j=1 for N; if \@.j.rank then iterate /*¿ocupado?*/
@.j.rank= 0; #= # - 1; file= j + 1; leave
end /*j*/
end /*while file>N*/
end /*while #<N*/
call show /*display the chess board with queens. */
exit 1 /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
nOK: say; say "No solution for" N 'queens.'; say; exit 0
/*──────────────────────────────────────────────────────────────────────────────────────*/
ok: parse arg f,r; fp= f + 1; rm= r - 1 /*if return≡0, then queen isn't safe. */
do k=1 for rm; if @.f.k then return 0; end
f= f-1; do k=rm by -1 for rm while f\==0; if @.f.k then return 0; f= f-1; end
f= fp; do k=rm by -1 for rm while f <=N; if @.f.k then return 0; f= f+1; end
return 1 /*1≡queen is safe. */ /* ↑↑↑↑↑↑↑↑ is queen under attack? */
/*──────────────────────────────────────────────────────────────────────────────────────*/
show: say 'A solution for ' N " queens:" /*display a title to the terminal.*/
g= substr( copies("╬═══", N) ,2) /*start of all cells on chessboard*/
say; say pad translate('╔'g"╗", '╦', "╬") /*display top rank (of the board).*/
line = '╠'g"╣"; dither= "▓"; ditherQ= '░' /*define a line for cell boundary.*/
bar = '║' ; queen = "Q" /*kinds: horiz., vert., salad.*/
Bqueen = ditherQ || queen || ditherQ /*glyph befitting a black square Q*/
Wqueen = ' 'queen" " /* " " " white " "*/
do rank=1 for N; if rank\==1 then say pad line; _= /*show rank sep. */
do file=1 for N
B = (file + rank) // 2 /*Is the square black ? Then B=1.*/
if B then Qgylph= Bqueen /*if black square, use dithered Q.*/
else Qgylph= Wqueen /* " white " " white " */
if @.file.rank then _= _ || bar || Qgylph /*Has queen? Use a 3─char Q symbol*/
else if B then _=_ || bar || copies(dither,3) /*dithering */
else _=_ || bar || copies( ' ' ,3) /* 3 blanks */
end /*file*/ /* [↑] preserve square─ish board.*/
say pad _ || bar /*show a single rank of the board.*/
end /*rank*/ /*80 cols can view a 19x19 board.*/
say pad translate('╚'g"╝", '╩', "╬"); return /*display the last rank (of board)*/