Algorithm to transform tree data in Ruby - ruby

Question

How can i change my tree made of Array of hashes into another structure such as:
My data looks like :
{
"A": [
{ "A1": [] },
{ "A2": [] },
{
"A3": [
{
"A31": [
{ "A311": [] },
{ "A312": [] }
]
}
]
}
]
}
into something like :
{
"name": "A",
"children": [
{ "name": "A1" },
{ "name": "A2" },
{
"name": "A3",
"children": [
{
"name": "A31",
"children": [
{ "name": "A311" },
{ "name": "A312" }
]
}
]
}
]
}
I tried a few things but nothing worked as I hoped.
This is how i move into my tree
def recursive(data)
return if data.is_a?(String)
data.each do |d|
keys = d.keys
keys.each do |k|
recursive(d[k])
end
end
return data
end
I tried my best to follow how to ask so to clarify :
The tree can have a unlimited deeph
Names are more complexe than A1, A2 ...

Answer 1

λ = ->(h) { [h[:name], h[:children] ? h[:children].map(&λ).to_h : []] }
[λ.(inp)].to_h
#⇒ {
# "A" => {
# "A1" => [],
# "A2" => [],
# "A3" => {
# "A31" => {
# "A311" => [],
# "A312" => []
# }
# }
# }
# }
This solution returns hashes that are not wrapped in arrays inside. If you really want to wrap nested hashes with arrays, map them in λ.

Answer 2

When you don't know how to implement something, always think the simplest case first.
Step 1: Convert {"A1" => []} to{"name" => "A1", "children" => []}
This is simple
def convert(hash)
pair = hash.each_pair.first
["name", "children"].zip(pair).to_h
end
Step2: Recursively convert all hashes in children
def convert(hash)
pair = hash.each_pair.first
pair[1] = pair[1].map{|child| convert(child)}
["name", "children"].zip(pair).to_h
end
Step 3: Handle corner cases
If children is empty then omit it.
def convert(hash)
pair = hash.each_pair.first
pair[1] = pair[1].map{|child| convert(child)}
result = {"name" => pair[0]}
result.merge!("children" => pair[1]) if pair[1].any?
result
end