Data commit

Task/Hamming-numbers/Common-Lisp/hamming-numbers-1.lisp

@@ -0,0 +1,20 @@
+(defun next-hamm (factors seqs)
+  (let ((x (apply #'min (map 'list #'first seqs))))
+    (loop for s in seqs
+	  for f in factors
+	  for i from 0
+	  with add = t do
+	  (if (= x (first s)) (pop s))
+	  ;; prevent a value from being added to multiple lists
+	  (when add
+	    (setf (elt seqs i) (nconc s (list (* x f))))
+	    (if (zerop (mod x f)) (setf add nil)))
+    finally (return x))))
+
+(loop with factors = '(2 3 5)
+      with seqs    = (loop for i in factors collect '(1))
+      for n from 1 to 1000001 do
+      (let ((x (next-hamm factors seqs)))
+	(if (or (< n 21)
+		(= n 1691)
+		(= n 1000000)) (format t "~d: ~d~%" n x))))

Task/Hamming-numbers/Common-Lisp/hamming-numbers-2.lisp

@@ -0,0 +1,20 @@
+(defun hamming (n)
+  (let ((fac '(2 3 5))
+	(idx (make-array 3 :initial-element 0))
+	(h (make-array (1+ n)
+		       :initial-element 1
+		       :element-type 'integer)))
+    (loop for i from 1 to n
+	  with e with x = '(1 1 1) do
+	  (setf e (setf (aref h i) (apply #'min x))
+		x (loop for y in x
+			for f in fac
+			for j from 0
+			collect (if (= e y) (* f (aref h (incf (aref idx j)))) y))))
+    (aref h n)))
+
+(loop for i from 1 to 20 do
+      (format t "~2d: ~d~%" i (hamming i)))
+
+(loop for i in '(1691 1000000) do
+      (format t "~d: ~d~%" i (hamming i)))