Data commit

Task/Permutations/Common-Lisp/permutations-1.lisp

@@ -0,0 +1,9 @@
+(defun permute (list)
+  (if list
+    (mapcan #'(lambda (x)
+		(mapcar #'(lambda (y) (cons x y))
+			(permute (remove x list))))
+	    list)
+    '(()))) ; else
+
+(print (permute '(A B Z)))

Task/Permutations/Common-Lisp/permutations-2.lisp

@@ -0,0 +1,18 @@
+(defun next-perm (vec cmp)  ; modify vector
+  (declare (type (simple-array * (*)) vec))
+  (macrolet ((el (i) `(aref vec ,i))
+             (cmp (i j) `(funcall cmp (el ,i) (el ,j))))
+    (loop with len = (1- (length vec))
+       for i from (1- len) downto 0
+       when (cmp i (1+ i)) do
+         (loop for k from len downto i
+            when (cmp i k) do
+              (rotatef (el i) (el k))
+              (setf k (1+ len))
+              (loop while (< (incf i) (decf k)) do
+                   (rotatef (el i) (el k)))
+              (return-from next-perm vec)))))
+
+;;; test code
+(loop for a = "1234" then (next-perm a #'char<) while a do
+     (write-line a))

Task/Permutations/Common-Lisp/permutations-3.lisp

@@ -0,0 +1,14 @@
+(defun heap-permutations (seq)
+  (let ((permutations nil))
+    (labels ((permute (seq k)
+	       (if (= k 1)
+		   (push seq permutations)
+		   (progn
+		     (permute seq (1- k))
+		     (loop for i from 0 below (1- k) do
+			  (if (evenp k)
+			      (rotatef (elt seq i) (elt seq (1- k)))
+			      (rotatef (elt seq 0) (elt seq (1- k))))
+			  (permute seq (1- k)))))))
+      (permute seq (length seq))
+      permutations)))