Nesting a given array into children, based on condition [closed] - ruby

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I have an array like this:
tweets = [
{
:user_id => 234567,
:username => "A",
:created_at => "2012-10-12 10:20:30"
},
{
:user_id => 234568,
:username => "B",
:created_at => "2012-10-12 10:20:34"
},
{
:user_id => 234569,
:username => "C",
:created_at => "2012-10-12 10:20:35"
},
{
:user_id => 234570,
:username => "D",
:created_at => "2012-10-12 10:20:40"
}
]
and another array, like this:
followers = [
{
:user_id => 234567,
:follower_ids => [234568, 56654]
},
{
:user_id => 234568,
:follower_ids => [234569, 454445]
},
{
:user_id => 234569,
:follower_ids => [234570, 56333]
},
{
:user_id => 234570,
:follower_ids => [45566, 61145]
}
]
I want to nest it into a deep structure, where one is made into children of another. For making the children, the condition to be satisfied is:
any other tweet which has a greater created_at than the other, and
whose user_id is included in the follower_ids list if that tweet in
the followers array is considered to be a child
and the expected output for the given data is like this:
arranged_tweets = [
{
:user_id => 234567,
:username => "A",
:created_at => "2012-10-12 10:20:30",
:children => [
{
:user_id => 234568,
:username => "B",
:created_at => "2012-10-12 10:20:34",
:children => [
{
:user_id => 234569,
:username => "C",
:created_at => "2012-10-12 10:20:35",
:children => [
{
:user_id => 234570,
:username => "D",
:created_at => "2012-10-12 10:20:40"
}
]
}
]
}
]
}
]

Answer 1

Untested, but should give you the idea:
arranged_tweets = tweets.collect do |tweet|
arranged_tweet(tweet, tweets - [tweet])
end
def arranged_tweet(tweet, other_tweets)
{ :user_id => tweet[:user_id], ...
:children => children(tweet, other_tweets) }
end
def children(tweet, other_tweets)
other_tweets.find_all { |other| is_child?(other, tweet) }.collect do |other|
arranged_tweet(other, other_tweets - [other])
end
end
def is_child?(tweet, parent_tweet)
parent_tweet[:created_at] > tweet[:created_at] &&
is_follower?(tweet[:user_id], parent_tweet[:user_id])
end
def is_follower?(user_id, other_user_id)
followers[other_user_id][:follower_ids].include?(user_id)
end