Tree traversal: Difference between revisions

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=={{header|Lua}}==

<syntaxhighlight lang="lua">~~-- Utility~~

local function ~~append~~(t1, t2)

local function depth_first(tr, a, b, c, flat_list)

for _, v in ipairs(t2) do

for _, val in ipairs({a, b, c}) do

if type(tr[val]) == "table" then

⚫

table.insert(t1, v)

depth_first(tr[val], a, b, c, flat_list)

⚫

end

elseif type(tr[val]) ~= "nil" then

⚫

table.insert(flat_list, tr[val])

end -- if

end -- for

return flat_list

end

local function flatten_pre_order(tr) return depth_first(tr, 1, 2, 3, {}) end

local function flatten_in_order(tr) return depth_first(tr, 2, 1, 3, {}) end

local function flatten_post_order(tr) return depth_first(tr, 2, 3, 1, {}) end

local function flatten_level_order(tr)

-- Node class

local ~~Node~~ = {}

local flat_list, queue = {}, {tr}

⚫

while next(queue) do -- while queue is not empty

Node.__index = Node

⚫

local node = table.remove(queue, 1) -- dequeue

if type(node) == "table" then

function Node:order(order)

⚫

table.insert(flat_list, node[1])

local r = {}

⚫

table.insert(queue, node[2]) -- enqueue

append(r, type(self[order[1]]) == "table" and self[order[1]]:order(order) or {self[order[1]]})

table.insert(queue, node[3]) -- enqueue

append(r, type(self[order[2]]) == "table" and self[order[2]]:order(order) or {self[order[2]]})

else

append(r, type(self[order[3]]) == "table" and self[order[3]]:order(order) or {self[order[3]]})

⚫

table.insert(flat_list, node)

⚫

return r

end

end -- if

⚫

end -- while

⚫

return flat_list

function Node:levelorder()

local levelorder = {}

local queue = {self}

⚫

while next(queue) do

⚫

local node = table.remove(queue, 1)

⚫

table.insert(~~levelorder~~, node[1])

⚫

table.insert(~~queue~~, ~~node~~[2])

⚫

table.insert(queue, node[3])

end

return levelorder

end

-- Node creator

local function new(value, left, right)

return value and setmetatable({

value,

(type(left) == "table") and new(unpack(left)) or new(left),

(type(right) == "table") and new(unpack(right)) or new(right),

}, Node) or nil

end

-- Example

local tree = ~~new(~~1, {2, {4, 7}, 5}, {3, {6, 8, 9}})

local tree = {1, {2, {4, 7}, 5}, {3, {6, 8, 9}}}

print("~~preorder~~: " .. table.concat(tree~~:order({1, 2, 3}~~), " "))

print("Pre order: " .. table.concat(flatten_pre_order(tree), " "))

print("~~inorder~~: " .. table.concat(tree~~:order({2, 1, 3}~~), " "))

print("In order: " .. table.concat(flatten_in_order(tree), " "))

print("~~postorder~~: " .. table.concat(tree~~:order({2, 3, 1}~~), " "))

print("Post order: " .. table.concat(flatten_post_order(tree), " "))

print("~~level-~~order: " .. table.concat(~~tree:levelorder~~(), " "))~~</syntaxhighlight>~~

print("Level order: " .. table.concat(flatten_level_order(tree), " "))

</syntaxhighlight>

=={{header|M2000 Interpreter}}==