binary tree levels

bad

bintree-levels.lisp

@@ -0,0 +1,36 @@
+(defstruct node
+  data
+  (l nil :type (or null node))
+  (r nil :type (or null node)))
+
+(defun node (data &optional l r)
+  (make-node :data data :l l :r r))
+
+;;     1
+;;    / \
+;;   2   3
+;;  / \ 
+;; 4   5
+(defparameter example
+  (node 1
+    (node 2
+      (node 4)
+      (node 5))
+    (node 3)))
+
+(defun maplonger (f alist blist)
+  (loop for a = alist then (cdr a)
+        for b = blist then (cdr b)
+        while (or (car a) (car b))
+        collecting (funcall f (car a) (car b))))
+
+(defun levels (node)
+  (if node
+      (with-slots (data l r) node
+        (cons (list data)
+              (maplonger #'nconc (levels l) (levels r))))
+      nil))
+
+(defun print-levels (node)
+  (loop for level in (levels node)
+        do (format t "~{~a~^ ~}~%" level)))