tasks a-s

Task/N-queens-problem/BCPL/n-queens-problem-1.bcpl

@@ -0,0 +1,30 @@
+// This can be run using Cintcode BCPL freely available from www.cl.cam.ac.uk/users/mr10.
+
+GET "libhdr.h"
+
+GLOBAL { count:ug; all  }
+
+LET try(ld, row, rd) BE TEST row=all
+
+                        THEN count := count + 1
+
+                        ELSE { LET poss = all & ~(ld | row | rd)
+                               WHILE poss DO
+                               { LET p = poss & -poss
+                                 poss := poss - p
+                                 try(ld+p << 1, row+p, rd+p >> 1)
+                               }
+                             }
+
+LET start() = VALOF
+{ all := 1
+
+  FOR i = 1 TO 16 DO
+  { count := 0
+    try(0, 0, 0)
+    writef("Number of solutions to %i2-queens is %i7*n", i, count)
+    all := 2*all + 1
+  }
+
+  RESULTIS 0
+}