CODEWITHSUNDEEP
arraysruby
Headmaster
Headmaster

Reputation: 2322

Iterate through two dimensional array while changing each element

I want to fill a two dimensional array with certain values. I want to get:

[
  ['Num00', 'Num01', 'Num02'],
  ['Num10', 'Num11', 'Num12'],
  ['Num20', 'Num21', 'Num22']
]

How can I do it?

This is my code:

game_field = Array.new(3, Array.new(3))
3.times do |i|
  3.times do |j|
    game_field[i][j] = 'Num' + i.to_s + j.to_s
  end
end
game_field

Upvotes: 0

Views: 126

Answers (7)

Mark Thomas
Mark Thomas

Reputation: 37507

Just a note that building a Matrix is simple because it has an inherent notion of rows and columns:

Matrix.build(3){|i,j| "Num#{i}#{j}"}

I think the Matrix class is often overlooked. The built-in methods to operate on rows, columns, submatrices, etc, can sometimes be really handy.

Upvotes: 3

Sagar Pandya
Sagar Pandya

Reputation: 9497

Well using Eric and Sawa's answer along with repeated_permutation we have

[0,1,2].repeated_permutation(2)
       .map { |a, b| "Num#{a}#{b}" }
       .each_slice(3).to_a

Upvotes: 0

steenslag
steenslag

Reputation: 80065

Ternary numbers?

(0...9).map{|n| "Num#{n.to_s(3).rjust(2,"0")}"}.each_slice(3).to_a

Upvotes: 1

Salil
Salil

Reputation: 47472

you can also try 

game_field = (0..2).map do |i|
  (0..2).map do |j|
    "Num#{i}#{j}"
  end
end

One liner 

game_field = (0..2).map {|i| (0..2).map {|j|  "Num#{i}#{j}"} }

Upvotes: 1

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

Just out of curiosity:

([(?0..?2)] * 2).
  map(&:to_a).
  reduce(:product).
  each_slice(3).
  map { |e| e.map(&:join).map(&'Num'.method(:+)) }

Upvotes: 2

sawa
sawa

Reputation: 168081

9.times.map{|i| "Num#{i.divmod(3).join}"}.each_slice(3).to_a

Upvotes: 1

Eric Duminil
Eric Duminil

Reputation: 54223

Array.new accepts a block in which you can define the element directly:

Array.new(3){|i| Array.new(3){|j| "Num#{i}#{j}" } }
# [["Num00", "Num01", "Num02"], ["Num10", "Num11", "Num12"], ["Num20", "Num21", "Num22"]]

When you call Array.new(3, Array.new(3)), you create an array which contains 3 times the exact same object : Array.new(3). When you modify an element in an inner-array, you modify it on every array!

If you initialize game_field like this : game_field = Array.new(3){ Array.new(3) }, your code works fine.

Upvotes: 6

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