How to initialize all the values of a two dimensional array using Ruby, is there any way to do it in 1 step?

Question

For example, initialize the entire array to 0 or any other value.

[
  [0, 0, 0, 0],
  [0, 0, 0, 0], 
  [0, 0, 0, 0]
]

Does this answer your question? How do I assign default values for two-dimensional array? — pjs
– pjs, Commented Nov 11, 2020 at 22:56

Ursus · Accepted Answer · 2020-11-11 22:42:22Z

3

Sure

Array.new(3) { Array.new(4, 0) }
 => [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]

answered Nov 11, 2020 at 22:42

Ursus

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6 Comments

Cary Swoveland Over a year ago

Eduard, a variant of this answer is Array.new(3) { Array.new(4) { 0 } }. You need to understand that this answer is not the same as arr = Array.new(3, Array.new(4, 0)) #=> [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]. The latter would be incorrect, for if we set arr[0][0] = 1 we would find arr #=> [[1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0]]. See Array::new.

user1934428 Over a year ago

@CarySwoveland : May I suggest thta you post this as answer instead of a comment, because this seems to really be the anwer to the OPs problem.

Stefan Over a year ago

@CarySwoveland putting 0 in an extra block is superfluous because integers are immutable. Ursus' answer is perfectly fine.

Ursus Over a year ago

Yeah, obviously I tried and there is no need for the extra block

Cary Swoveland Over a year ago

@Stefan and Ursus, I was not advocating the variant; I mentioned it only to alert Eduard in case he saw it written that way.

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