Print out 2D array

Question

array = Array.new(10) { Array.new(10 , 0)}

array.each { |x| print x }

Prints out one single line of ten [0, 0, 0, 0, 0, 0, 0, 0, 0, 0].

If I were to change print to puts, I then get 100 0 down the page.

How do I print out each array on a separate line without the "[]" and ","?

Something like:

0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0

Answer 1

Suppose:

arr = Array.new(10) { (0..20).to_a.sample(10) }

Then

puts arr.map { |x| x.join(' ') }
1 9 6 15 7 19 18 3 0 12
13 20 18 15 0 3 19 1 14 16
7 16 5 3 12 19 4 9 20 10
6 10 9 1 18 17 7 19 5 15
12 3 8 16 10 5 2 18 20 6
12 9 0 18 2 11 16 8 7 15
8 9 14 19 3 16 6 20 13 17
7 19 16 14 13 6 9 2 3 5
10 17 8 15 11 2 13 14 16 7
14 9 20 17 15 3 4 2 11 19

is not very, er, attractive. For something more pleasing, you could quite easily do something like this:

width = arr.flatten.max.to_s.size+2
  #=> 4
puts arr.map { |a| a.map { |i| i.to_s.rjust(width) }.join }
   1   9   6  15   7  19  18   3   0  12
  13  20  18  15   0   3  19   1  14  16
   7  16   5   3  12  19   4   9  20  10
   6  10   9   1  18  17   7  19   5  15
  12   3   8  16  10   5   2  18  20   6
  12   9   0  18   2  11  16   8   7  15
   8   9  14  19   3  16   6  20  13  17
   7  19  16  14  13   6   9   2   3   5
  10  17   8  15  11   2  13  14  16   7
  14   9  20  17  15   3   4   2  11  19

If you have too many columns to display on the screen you can do this:

puts arr.map { |a| a.map { |i| i.to_s.rjust(width) }.join.tinyfy }

    1   9   6  15   7  19  18   3   0  12
   13  20  18  15   0   3  19   1  14  16
    7  16   5   3  12  19   4   9  20  10
    6  10   9   1  18  17   7  19   5  15
   12   3   8  16  10   5   2  18  20   6
   12   9   0  18   2  11  16   8   7  15
    8   9  14  19   3  16   6  20  13  17
    7  19  16  14  13   6   9   2   3   5
   10  17   8  15  11   2  13  14  16   7
   14   9  20  17  15   3   4   2  11  19

Answer 2

Try join:

array.each { |x|
 puts x.join(" ")
}
# prints:
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0

Answer 3

You may want to write your own method to do it. Something like:

def array_2D_print array
    array.each do |arr|
        arr.each do |item|
            print "#{item} "
        end
        print "\n"
    end
end

If you only use this once in your code, you might also consider not creating any method:

array.each do |arr|
    arr.each do |item|
        print "#{item} "
    end
    print "\n"
end

This solution has the advantage of being easier to modify than other alternatives, to match what you want to print.

Answer 4

Print a 2-dimensional array with spacing between columns

Accepts a 2d array of objects that have a to_s method (strings integers floats and booleans..) and an optional margin width integer.

Update: It now works with arrays of varying lengths.

def print_table(table, margin_width = 2)
  # the margin_width is the spaces between columns (use at least 1)

  column_widths = []
  table.each do |row|
    row.each.with_index do |cell, column_num|
      column_widths[column_num] = [column_widths[column_num] || 0, cell.to_s.size].max
    end
  end

  puts (table.collect do |row|
    row.collect.with_index do |cell, column_num|
      cell.to_s.ljust(column_widths[column_num] + margin_width)
    end.join
  end)
end

Note: the parenthesis after the puts statement is required so table.collect and the do end block are not passed as two separate parameters to the puts method.

Example table

my_table = [
  ["1", "Animal", "Dog", "1"],
  [1, "Animal", "Cat", "2"],
  [1, "Animal", "Bird", "3"],
  [2, "Place", "USA", "1"],
  [2.5, "Place", "Other", "2"],
  [3, "Color", "Red"],
  [3, "Color", "Blue", "b"],
  [3, "Some more color", "Orange", "c"],
  [4.7, "Age", "Young", "a"],
  [4, "Age", "Middle", "b"],
  [4, "Age", "Old", "c"],
  [5, "Alive"],
  [],
  [5, "Alive", false, "n"]
]

print_table my_table

Prints:

1    Animal           Dog     1  
1    Animal           Cat     2  
1    Animal           Bird    3  
2    Place            USA     1  
2.5  Place            Other   2  
3    Color            Red     
3    Color            Blue    b  
3    Some more color  Orange  c  
4.7  Age              Young   a  
4    Age              Middle  b  
4    Age              Old     c  
5    Alive            

5    Alive            false   n 

(Not colored. The coloring above was added by StackOverflow.)