Project Euler 11: Ruby

In my attempt to learn Ruby out in the open, here’s my solution for Project Euler Problem 11. I previously solved this problem in F# and it nearly killed me. Since I knew the ins and outs of the problem already, it didn’t take much to port the F# code over to Ruby. That said, I’m sure the code can be improved. Any suggestions? As always, any feedback is welcome.

# Euler 11
# http://projecteuler.net/index.php?section=problems&id=11
# What is the greatest product
# of four adjacent numbers in any direction (up, down, left,
# right, or diagonally) in the 20 x 20 grid?
timer_start = Time.now

numbers = \
"08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48"

# split on newline character
rows = numbers.split("\n")

# split rows into two dimensional array and convert to int
grid = rows.map { |x| x.split(" ") \
  .map { |x| x.to_i } }

# left and right
max, product = 0, 0
(0...16).each do |x|
  (0...19).each do |y|
    product = grid[y][x] * grid[y][x+1] * \
      grid[y][x+2] * grid[y][x+3]
    max = product if product > max
  end
end 

# up and down
(0...19).each do |x|
  (0...16).each do |y|
    product = grid[y][x] * grid[y+1][x] * \
      grid[y+2][x] * grid[y+3][x]
    max = product if product > max
  end
end 

# diagonal right
(0...16).each do |x|
  (0...16).each do |y|
    product = grid[y][x] * grid[y+1][x+1] * \
      grid[y+2][x+2] * grid[y+3][x+3]
    max = product if product > max
  end
end 

# diagonal left
(0...16).each do |x|
  (0...16).each do |y|
    product = grid[y][x+3] * grid[y+1][x+2] * \
      grid[y+2][x+1] * grid[y+3][x]
    max = product if product > max
  end
end 

puts max
puts "Elapsed Time: #{(Time.now - timer_start)*1000} milliseconds"