tehee

sudoku.lispbm

@@ -27,6 +27,17 @@
 (defun amount (x y)
   (foldr (lambda (z q) (if (eq x z) (+ q 1) q)) 0 y))
 
+(defun in (x xs) (foldr (lambda (y z) (if (eq x y) t z)) nil xs))
+
+(defun intersection (xs ys) (filter (lambda (x) (in x ys)) xs))
+
+(defun repeat (x e)
+  (if (number? x)
+    (match x
+        (0 nil)
+        (_ (cons e (repeat (- x 1) e))))
+    'error))
+
 (defun valid (x)
     (if (= 9 (length x))
         (foldr
@@ -35,8 +46,36 @@
             (map (lambda (y) (amount y x)) nums))
         nil))
 
+(defun notPresentRow (xs)
+  (foldr
+   (lambda (x ys) (if (in x xs) ys (cons x ys)))
+   nil
+   nums))
+
+(defun notPresent (grid row col)
+  (intersection (notPresentRow (getRow grid row))
+                (notPresentRow (getCol grid col))))
+
 (defun getRow (grid x) (ix grid x))
 
+(defun findEmpty (grid)
+  (foldr (lambda (zs ys)
+           (match zs
+            (((?row) . (?rowVal))
+                (append
+                 (zip
+                    (repeat 9 row)
+                    (foldr (lambda (x qs)
+                            (match x
+                                   (((?col) . (?val)) (if (eq val nil) (cons col qs) qs))
+                                   (_ 'error)))
+                           nil
+                           (zip (iota 9) rowVal)))
+                 ys))
+            (_ 'error)))
+         nil
+         (zip (iota 9) grid)))
+
 (defun transpose (grid)
   (match grid
     (nil nil)