Data commit

Task/N-queens-problem/Run-BASIC/n-queens-problem.basic

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+[loop]
+input "How many queens (N>=4)";n
+if n < 4 then
+ print "Must be greater than 4"
+ goto [loop]
+end if
+
+dim plot$(100,100)
+dim q(n+20)
+dim e(n+20)
+dim o(n+20)
+r=n mod 6
+if r<>2 and r<>3 then
+  gosub [samp]
+  goto [shoBoard]
+end if
+for i=1 to int(n/2)
+  e(i) = 2 * i
+next
+for i=1 to int((n/2)+.5)
+ o(i) = 2 *i-1
+next
+if r = 2 then gosub [edt2]
+if r = 3 then gosub [edt3]
+s = 1
+for i=1 to n
+  if e(i)>0 then
+    q(s) = e(i)
+    s    = s+1
+  end if
+next
+for i=1 to n
+  if o(i) > 0 then
+    q(s) = o(i)
+    s    = s + 1
+  end if
+next
+' print board
+[shoBoard]
+cls
+for i = 1 to n
+  plot$(i,26-q(i)) = "*"
+  plot$(i,24-n)    = chr$(96+i)
+  plot$(n+1,26-i)  = str$(i)
+next i
+for ii = 1 to 100
+ for jj = 1 to 100
+  print left$(plot$(jj,ii)+" ",1);
+ next jj
+print
+next ii
+end
+
+' the simple case
+[samp]
+p = 1
+for i = 1 to n
+  if i mod 2=0 then
+    q(p) = i
+    p    = p + 1
+  end if
+next i
+for i = 1 to n
+  if i mod 2 then
+    q(p) = i
+    p    = p + 1
+  end if
+next
+return
+' edit list when remainder is 2
+[edt2]
+for i=1 to n
+  if o(i) = 3 then
+    o(i) = 1
+   else
+    if o(i)=1 then o(i) = 3
+  end if
+  if o(i) = 5 then
+    o(i)= o(i) -1
+   else
+    if o(i) = 0 then
+      o(i) = 5
+      return
+    end if
+  end if
+next
+
+' edit list when remainder is 3
+[edt3]
+for i = 1 to n
+  if e(i) = 2 then
+    e(i)  = e(i)-1
+   else
+    if e(i) = 0 then
+      e(i) = 2
+      goto [more]
+    end if
+  end if
+next i
+' edit list some more
+[more]
+for i = 1 to n
+  if (o(i)=1 or o(i)=3) then
+    o(i) = o(i)-1
+   else
+    if o(i) = 0 then
+      o(i)   = 1
+      o(i+1) = 3
+      return
+    end if
+  end if
+next