Data commit

Task/Tree-traversal/REBOL/tree-traversal.rebol

@@ -0,0 +1,46 @@
+tree: [1 [2 [4 [7 [] []] []] [5 [] []]] [3 [6 [8 [] []] [9 [] []]] []]]
+; "compacted" version
+tree: [1 [2 [4 [7  ] ] [5  ]] [3 [6 [8  ] [9  ]] ]]
+
+visit: func [tree [block!]][prin rejoin [first tree " "]]
+left: :second
+right: :third
+
+preorder: func [tree [block!]][
+	if not empty? tree [visit tree]
+	attempt [preorder left tree]
+	attempt [preorder right tree]
+]
+prin "preorder:    " preorder tree
+print ""
+
+inorder: func [tree [block!]][
+	attempt [inorder left tree]
+	if not empty? tree [visit tree]
+	attempt [inorder right tree]
+]
+prin "inorder:     " inorder tree
+print ""
+
+postorder: func [tree [block!]][
+	attempt [postorder left tree]
+	attempt [postorder right tree]
+	if not empty? tree [visit tree]
+]
+prin "postorder:   " postorder tree
+print ""
+
+queue: []
+enqueue: func [tree [block!]][append/only queue tree]
+dequeue: func [queue [block!]][take queue]
+level-order: func [tree [block!]][
+	clear head queue
+	queue: enqueue tree
+	while [not empty? queue] [
+		tree: dequeue queue
+		if not empty? tree [visit tree]
+		attempt [enqueue left tree]
+		attempt [enqueue right tree]
+	]
+]
+prin "level-order: " level-order tree