CODEWITHSUNDEEP
arraysruby
kms
kms

Reputation: 1

Find multiple indexes in a multidimensional array

I'm trying to find the indexes where a specific string is located in a multidimensional array in Ruby. I'm using the following code. 

array = [['x', 'x',' x','x'],
         ['x', 'S',' ','x'],
         ['x', 'x','x','S']]

array.index(array.detect{|aa| aa.include?('S')}

However, this only returns 1 (the first index). Does anyone know how I can alter this command to return all the indexes where the pattern is present? This example should return 1 and 2.

Upvotes: 0

Views: 160

Answers (2)

Cary Swoveland
Cary Swoveland

Reputation: 110665

One way:

array = [['x', 'x',' x','x'],
         ['x', 'S',' ','x'],
         ['x', 'x','x','S']]

array.each_with_index.with_object([]) do |(row,i),arr|
  j = row.index('S')
  arr << i unless j.nil?
end
  #=> [1, 2]

It's only a small change to retrieve both the row and column indices (assuming there is at most one target string per row):

array.each_with_index.with_object([]) do |(row,i),arr|
  j = row.index('S')
  arr << [i,j] unless j.nil?
end
  #=> [[1, 1], [2, 3]]

You can also use the Matrix class to obtain row/column pairs.

require 'matrix'

Matrix[*array].each_with_index.with_object([]) { |(e,i,j),arr| arr << [i,j] if e == 'S' }
  #=> [[1, 1], [2, 3]]

Upvotes: 0

Michael Kohl
Michael Kohl

Reputation: 66837

Here's the updated solution now that you updated your question and added the below comment:

array.each_index.select { |i| array[i].include?('S') }
#=> [1, 2]

Upvotes: 2

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