tasks a-s

Task/N-queens-problem/Pascal/n-queens-problem.pascal

@@ -0,0 +1,81 @@
+program queens;
+
+const l=16;
+
+var i,j,k,m,n,p,q,r,y,z: integer;
+    a,s: array[1..l] of integer;
+    u: array[1..4*l-2] of integer;
+
+label L3,L4,L5,L6,L7,L8,L9,L10;
+
+begin
+   for i:=1 to l do a[i]:=i;
+   for i:=1 to 4*l-2 do u[i]:=0;
+   for n:=1 to l do
+   begin
+      m:=0;
+      i:=1;
+      r:=2*n-1;
+      goto L4;
+L3:
+      s[i]:=j;
+      u[p]:=1;
+      u[q+r]:=1;
+      i:=i+1;
+L4:
+      if i>n then goto L8;
+      j:=i;
+L5:
+      z:=a[i];
+      y:=a[j];
+      p:=i-y+n;
+      q:=i+y-1;
+      a[i]:=y;
+      a[j]:=z;
+      if (u[p]=0) and (u[q+r]=0) then goto L3;
+L6:
+      j:=j+1;
+      if j<=n then goto L5;
+L7:
+      j:=j-1;
+      if j=i then goto L9;
+      z:=a[i];
+      a[i]:=a[j];
+      a[j]:=z;
+      goto L7;
+L8:
+      m:=m+1;
+      { uncomment the following to print solutions }
+      { write(n,' ',m,':');
+      for k:=1 to n do write(' ',a[k]);
+      writeln; }
+L9:
+      i:=i-1;
+      if i=0 then goto L10;
+      p:=i-a[i]+n;
+      q:=i+a[i]-1;
+      j:=s[i];
+      u[p]:=0;
+      u[q+r]:=0;
+      goto L6;
+L10:
+      writeln(n,' ',m);
+   end;
+end.
+
+{ 1 1
+  2 0
+  3 0
+  4 2
+  5 10
+  6 4
+  7 40
+  8 92
+  9 352
+ 10 724
+ 11 2680
+ 12 14200
+ 13 73712
+ 14 365596
+ 15 2279184
+ 16 14772512 }