euler-011

require 'matrix'

grid = Matrix[[8,2,22,97,38,15,0,40,0,75,4,5,7,78,52,12,50,77,91,8],
           [49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,4,56,62,0],
           [81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,3,49,13,36,65],
           [52,70,95,23,4,60,11,42,69,24,68,56,1,32,56,71,37,2,36,91],
           [22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80],
           [24,47,32,60,99,3,45,2,44,75,33,53,78,36,84,20,35,17,12,50],
           [32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70],
           [67,26,20,68,2,62,12,20,95,63,94,39,63,8,40,91,66,49,94,21],
           [24,55,58,5,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72],
           [21,36,23,9,75,0,76,44,20,45,35,14,0,61,33,97,34,31,33,95],
           [78,17,53,28,22,75,31,67,15,94,3,80,4,62,16,14,9,53,56,92],
           [16,39,5,42,96,35,31,47,55,58,88,24,0,17,54,24,36,29,85,57],
           [86,56,0,48,35,71,89,7,5,44,44,37,44,60,21,58,51,54,17,58],
           [19,80,81,68,5,94,47,69,28,73,92,13,86,52,17,77,4,89,55,40],
           [4,52,8,83,97,35,99,16,7,97,57,32,16,26,26,79,33,27,98,66],
           [88,36,68,87,57,62,20,72,3,46,33,67,46,55,12,32,63,93,53,69],
           [4,42,16,73,38,25,39,11,24,94,72,18,8,46,29,32,40,62,76,36],
           [20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,4,36,16],
           [20,73,35,29,78,31,90,1,74,31,49,71,48,86,81,16,23,57,5,54],
           [1,70,54,71,83,51,54,69,16,92,33,48,61,43,52,1,89,19,67,48]]

# Calculate product of four adjacent numbers in a given direction
def calculate_product(grid, row, col, row_step, col_step)
  (0..3).map { |i| grid[row + i*row_step, col + i*col_step] }.reduce(:*)
rescue IndexError
  nil  # Return nil if we go out of bounds
end

# Define the directions to check: right, down, diagonal right, diagonal left
DIRECTIONS = [
  [0, 1],  # Right
  [1, 0],  # Down
  [1, 1],  # Diagonal right-down
  [1, -1]  # Diagonal left-down
]

# Find the maximum product
max_product = 0
grid.each_with_index do |_, row, col|
  DIRECTIONS.each do |row_step, col_step|
    product = calculate_product(grid, row, col, row_step, col_step)
    max_product = [max_product, product].compact.max
  end
end

puts "The greatest product of four adjacent numbers is: #{max_product}"
    results << grid.[](x, y).to_i * grid.[](x-1, y+1).to_i * grid.[](x-2, y+2).to_i * grid.[](x-3, y+3).to_i
  end
end
puts results.max