How do I read a text file into an array of array (each sub-array being a row in the text file?)

Question

so I'm pretty much a n00b at Ruby, and I've put together a code to solve a MinCut problem (for an assignment, yes - that part of the code I've put together and tested), and I can't figure out how to read a file and put it into an array of arrays. I have a text file to read, with columns of varying length as below

1 37 79 164

2 123 134

3 48 123 134 109

and I'd like to read it into a 2D array, where each line and columnn is split, with each line going into one array. So the resulting array for the above example would be :

[[1, 37, 79, 164], [2, 123, 134], [3, 48, 123, 134, 109]]

My code to read the text file is below:

def read_array(file, count)
  int_array = []
  File.foreach(file) do |f|
    counter = 0
    while (l = f.gets and counter < count ) do
      temp_array = []
      temp_array << l.to_i.split(" ")
      int_array << temp_array
      counter = counter + 1
    end

  end
  return int_array
end

Any help is greatly appreciated!

Also, if it helps, the error I'm currently getting is "block in read_array': private method 'gets' called for # "

I've tried a few things, and have gotten different error messages though...

Answer 1

File.readlines('test.txt').map do |line|
  line.split.map(&:to_i)
end

Explanation

readlines reads the whole file and splits it by newlines. It looks like this:

["1 37 79 164\n", "2 123 134\n", "3 48 123 134 109"]

Now we iterate over the lines (using map) and split each line into its number parts (split)

[["1", "37", "79", "164"], ["2", "123", "134"], ["3", "48", "123", "134", "109"]]

The items are still strings, so the inner map converts them to integers (to_i).

[[1, 37, 79, 164], [2, 123, 134], [3, 48, 123, 134, 109]]