2016 Update

Task/Tree-traversal/AppleScript/tree-traversal-1.applescript

@@ -0,0 +1,88 @@
+on run
+    set tree to {1, {2, {4, {7}, {}}, {5}}, {3, {6, {8}, {9}}, {}}}
+
+    return {|pre-order|:¬
+        traverse("pre-order", tree), |in-order|:¬
+        traverse("in-order", tree), |post-order|:¬
+        traverse("post-order", tree), |level-order|:¬
+        traverse("level-order", tree)}
+
+end run
+
+-- traverse :: String -> Tree -> [Int]
+on traverse(strOrderName, tree)
+    if strOrderName does not start with "level" then
+        set {v, l, r} to nodeParts(tree)
+
+        if l is {} then
+            set lstLeft to []
+        else
+            set lstLeft to traverse(strOrderName, l)
+        end if
+
+        if r is {} then
+            set lstRight to []
+        else
+            set lstRight to traverse(strOrderName, r)
+        end if
+
+        -- PRE-ORDER
+        if strOrderName begins with "pre" then
+            v & lstLeft & lstRight
+
+            -- IN-ORDER
+        else if strOrderName begins with "in" then
+            lstLeft & v & lstRight
+
+            -- POST-ORDER
+        else if strOrderName begins with "post" then
+            lstLeft & lstRight & v
+
+        end if
+    else
+        -- LEVEL-ORDER
+        levelOrder({tree})
+    end if
+end traverse
+
+
+-- levelOrder :: [Tree] -> [Int]
+on levelOrder(lstTree)
+    if length of lstTree > 0 then
+        set {head, tail} to uncons(lstTree)
+
+        -- Take any value found in the head node
+        -- deferring any child nodes to the end of the tail
+        -- before recursing
+
+        if head is not {} then
+            set {v, l, r} to nodeParts(head)
+            v & levelOrder(tail & {l, r})
+        else
+            levelOrder(tail)
+        end if
+    else
+        {}
+    end if
+end levelOrder
+
+-- nodeParts :: Tree -> (Int, Tree, Tree)
+on nodeParts(tree)
+    if class of tree is list and length of tree = 3 then
+        tree
+    else
+        {tree} & {{}, {}}
+    end if
+end nodeParts
+
+
+-- GENERIC
+
+-- uncons :: [a] -> Maybe (a, [a])
+on uncons(xs)
+    if length of xs > 0 then
+        {item 1 of xs, rest of xs}
+    else
+        missing value
+    end if
+end uncons

Task/Tree-traversal/AppleScript/tree-traversal-2.applescript

@@ -0,0 +1,4 @@
+{|pre-order|:{1, 2, 4, 7, 5, 3, 6, 8, 9},
+|in-order|:{7, 4, 2, 5, 1, 8, 6, 9, 3},
+|post-order|:{7, 4, 5, 2, 8, 9, 6, 3, 1},
+|level-order|:{1, 2, 3, 4, 5, 6, 7, 8, 9}}