How do I flatten an array in Ruby?

Question

On Ruby. I have array of array c = [["a"], ["b"]]

How convert it to c = a + b

c = ["a", "b"]

for any array. Maybe it is possible not using other variables. All array inside not flatten.

d = [ [["a"], ["b"]], [["c"], ["d"]], [["e"], ["f"]] ]

I need [ [["a"], ["b"], ["c"], ["d"], ["e"], ["f"]] ]

flatten is not good for array of array . more deeper [[["a"], ["b"]]] i need flatter but only one step — Eliasz Łukasz
– Eliasz Łukasz, Commented Nov 23, 2017 at 10:45
I just edited the post to make the question clearer, I think you edited it too, you might need to do so again. — Kris
– Kris, Commented Nov 23, 2017 at 10:48
On the first example, the input array is 2 levels deep and the output is a flat array (1 level deep). On the second example both the input and the output arrays are 3 levels deep. What's the rule? — axiac
– axiac, Commented Nov 23, 2017 at 10:57

Santhosh · Accepted Answer · 2017-11-23 10:53:47Z

35

Array#flatten also accepts a parameter.

The optional level argument determines the level of recursion to flatten.

c = [[["a"]], [["b"]]]

c.flatten
# => ["a", "b"]

c.flatten(1)
# => [["a"], ["b"]]

answered Nov 23, 2017 at 10:53

Santhosh

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2 Comments

axiac Over a year ago

How can this be used to produce the outcome describe in the question (for both examples provided)?

Santhosh Over a year ago

@axiac flatten will produce outcome from the OP's 1st eg. The second example is a typo (input & output is same). What OP is looking for is 1 level flatten, which he has mentioned in the comments.

Mikhail Katrin · Accepted Answer · 2017-11-23 11:04:56Z

5

Use flatten

Returns a new array that is a one-dimensional flattening of this array (recursively). That is, for every element that is an array, extract its elements into the new array. If the optional level argument determines the level of recursion to flatten.

irb(main):001:0> a =  [["a"], ["b"]]
=> [["a"], ["b"]]
irb(main):002:0> a.flatten
=> ["a", "b"]

You can control level of recursion flatten(n):

irb(main):001:0> c = [[["a"]], [["b"]]]
=> [[["a"]], [["b"]]]
irb(main):002:0> c.flatten 1
=> [["a"], ["b"]]
irb(main):003:0>

edited Nov 23, 2017 at 11:04

answered Nov 23, 2017 at 10:45

Mikhail Katrin

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Comments

Sandip Mane · Accepted Answer · 2017-11-23 10:47:45Z

0

Ruby:

c = [["a"], ["b"]]

Convert Array of array to Array

c.flatten

To get the sum of array of array

c.flatten.sum

answered Nov 23, 2017 at 10:47

Sandip Mane

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3 Comments

Eliasz Łukasz Over a year ago

no. d = [ [["a"], ["b"]], [["c"], ["d"]], [["e"], ["f"]] ] => ["a", "b", "c", "d", "e", "f"] I need [ [["a"], ["b"], ["c"], ["d"], ["e"], ["f"]] ]

Eliasz Łukasz Over a year ago

this delete deeper structure, this is not answer

Sandip Mane Over a year ago

This will do it [d.flatten.collect { |x| [x] }]

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