I have an n-depth array where n is a variable greater than or equal to 2:
[[1,1],[[1,1],[1,1]]]
I want to flatten this array to have exactly 2 depth, like this:
[[1,1],[1,1],[1,1]]
Can anyone think of a good way to achieve that?
3 Answers
This should do it.
def flatten_after_first(arr)
arr.flat_map { |a| a.first.is_a?(Array) ? a.map(&:flatten) : [a] }
end
flatten_after_first [[1,1],[[1,1],[1,1]]]
#=> [[1, 1], [1, 1], [1, 1]]
flatten_after_first [[1,1], [[2,2], [2,2]], [[[3,3], [3,3]], [[3,3], [3,3]]]]
#=> [[1, 1], [2, 2], [2, 2], [3, 3, 3, 3], [3, 3, 3, 3]]
1 Comment
Mike S
Yeah, the OP threw everyone off by writing "depth first" in the title. The example he gave in the question is not the result you would get with depth first flatten. But it looks like your answer is what he wants.
May be this will help
def flat(array)
array.each do |item|
if item.is_a?(Array) && item.flatten.count != item.count
flat(item)
else
$arr << item
end
end
end
###
$arr = []
collection = [[1, 1], [[1, 1], [1, 1], [[1, 2], [1, 2, 3]]]]
flat(collection)
puts $arr.inspect
=> [[1, 1], [1, 1], [1, 1], [1, 2], [1, 2, 3]]
$arr = []
collection = [[1,1],[[[1,1],[1,1]],[1,1]]]
flat(collection)
$arr
=> [[1, 1], [1, 1], [1, 1], [1, 1]]
Comments
Try this:
def depth_first_flatten array
result = []
array.each do |element|
if element.first.is_a? Array
result += deph(element)
else
result << element
end
end
result
end
# array = [[1,2],[[3,4],[5,6]]]
# depth_first_flatten(array)
#
# OUTPUT: [[1, 2], [3, 4], [5, 6]]
3 Comments
Rafael Biriba
I also tested with:
array = [[1, 2], [[3, 4], [5, 6]], [[[[[7, 8], [9, 10]]]]]] with the output [[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]Rafael Biriba
Tested
array = [[1, 1], [[1, 1], [1, 1], [[1, 2], [1, 2, 3]]]] and output: [[1, 1], [1, 1], [1, 1], [1, 2], [1, 2, 3]]Rafael Biriba
Nice challenge! I liked!
[[1,1],[1,1]]become[1,1], [1,1]and not[1,1,1,1]?