918d929c09
To encourage organizing code in a way that helps in understanding, I have implemented the common idiom of requiring a `main` function. In tricu and other functional languages, it is usually placed near the top of the module. The evaluator gracefully handles the situation of passing multiple files where the intermediary "library" files do not have main functions.
62 lines
1.9 KiB
Plaintext
62 lines
1.9 KiB
Plaintext
main = exampleTwo
|
|
-- Level Order Traversal of a labelled binary tree
|
|
-- Objective: Print each "level" of the tree on a separate line
|
|
--
|
|
-- We model labelled binary trees as nested lists where values act as labels. We
|
|
-- require explicit notation of empty nodes. Empty nodes can be represented
|
|
-- with an empty list, `[]`, which evaluates to a single node `t`.
|
|
--
|
|
-- Example tree inputs:
|
|
-- [("1") [("2") [("4") t t] t] [("3") [("5") t t] [("6") t t]]]]
|
|
-- Graph:
|
|
-- 1
|
|
-- / \
|
|
-- 2 3
|
|
-- / / \
|
|
-- 4 5 6
|
|
|
|
label = \node : head node
|
|
|
|
left = (\node : if (emptyList? node)
|
|
[]
|
|
(if (emptyList? (tail node))
|
|
[]
|
|
(head (tail node))))
|
|
|
|
right = (\node : if (emptyList? node)
|
|
[]
|
|
(if (emptyList? (tail node))
|
|
[]
|
|
(if (emptyList? (tail (tail node)))
|
|
[]
|
|
(head (tail (tail node))))))
|
|
|
|
processLevel = y (\self queue : if (emptyList? queue)
|
|
[]
|
|
(pair (map label queue) (self (filter
|
|
(\node : not? (emptyList? node))
|
|
(lconcat (map left queue) (map right queue))))))
|
|
|
|
levelOrderTraversal_ = \a : processLevel (t a t)
|
|
|
|
toLineString = y (\self levels : if (emptyList? levels)
|
|
""
|
|
(lconcat
|
|
(lconcat (map (\x : lconcat x " ") (head levels)) "")
|
|
(if (emptyList? (tail levels)) "" (lconcat (t (t 10 t) t) (self (tail levels))))))
|
|
|
|
levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
|
|
|
|
flatten = foldl (\acc x : lconcat acc x) ""
|
|
|
|
levelOrderTraversal = \s : lconcat (t 10 t) (flatten (levelOrderToString s))
|
|
|
|
exampleOne = levelOrderTraversal [("1")
|
|
[("2") [("4") t t] t]
|
|
[("3") [("5") t t] [("6") t t]]]
|
|
|
|
exampleTwo = levelOrderTraversal [("1")
|
|
[("2") [("4") [("8") t t] [("9") t t]]
|
|
[("6") [("10") t t] [("12") t t]]]
|
|
[("3") [("5") [("11") t t] t] [("7") t t]]]
|