Data commit

Task/Tree-traversal/ACL2/tree-traversal.acl2

@@ -0,0 +1,47 @@
+(defun flatten-preorder (tree)
+   (if (endp tree)
+       nil
+       (append (list (first tree))
+               (flatten-preorder (second tree))
+               (flatten-preorder (third tree)))))
+
+(defun flatten-inorder (tree)
+   (if (endp tree)
+       nil
+       (append (flatten-inorder (second tree))
+               (list (first tree))
+               (flatten-inorder (third tree)))))
+
+(defun flatten-postorder (tree)
+   (if (endp tree)
+       nil
+       (append (flatten-postorder (second tree))
+               (flatten-postorder (third tree))
+               (list (first tree)))))
+
+(defun flatten-level-r1 (tree level levels)
+   (if (endp tree)
+       levels
+       (let ((curr (cdr (assoc level levels))))
+            (flatten-level-r1
+             (second tree)
+             (1+ level)
+             (flatten-level-r1
+              (third tree)
+              (1+ level)
+              (put-assoc level
+                         (append curr (list (first tree)))
+                         levels))))))
+
+(defun flatten-level-r2 (levels max-level)
+   (declare (xargs :measure (nfix (1+ max-level))))
+   (if (zp (1+ max-level))
+       nil
+       (append (flatten-level-r2 levels
+                                 (1- max-level))
+               (reverse (cdr (assoc max-level levels))))))
+
+
+(defun flatten-level (tree)
+   (let ((levels (flatten-level-r1 tree 0 nil)))
+      (flatten-level-r2 levels (len levels))))