euler/euler011.rb

require 'matrix'

def matrix_horizontal_consecutive(matrix)
  across_lists = []
  (0..matrix.row_count-1).each do |row_num|
    across_lists += consecutive_across_lists(matrix.row(row_num))
  end
  across_lists
end

def consecutive_across_lists(list)
  list_of_sub_lists = []
  start_index = 0
  end_index = 3
  while end_index < list.size
    list_of_sub_lists << list[start_index..end_index]
    start_index += 1
    end_index += 1
  end
  list_of_sub_lists
end

def matrix_vertical_consecutive(matrix)
  transpose = matrix.transpose
  matrix_horizontal_consecutive(transpose)
end

#right top to bottom
def right_diagonal_consecutive(matrix)
  diagonals = []
  i_0 = 0
  j_0 = 0
  i_1 = 1
  j_1 = 1
  i_2 = 2
  j_2 = 2
  i_3 = 3
  j_3 = 3
  while i_0 < matrix.row_count - 3
    while j_0 < matrix.column_count - 3
      diagonals << [matrix[i_0,j_0], matrix[i_1, j_1], matrix[i_2, j_2], matrix[i_3, j_3]]
      j_0 += 1
      j_1 += 1
      j_2 += 1
      j_3 += 1
    end
    j_0 = 0
    j_1 = 1
    j_2 = 2
    j_3 = 3
    i_0 += 1
    i_1 += 1
    i_2 += 1
    i_3 += 1
  end
  diagonals
end

#left top to bottom
def left_diagonal_consecutive(matrix)
  diagonals = []
  i_0 = 3
  j_0 = 0
  i_1 = 2
  j_1 = 1
  i_2 = 1
  j_2 = 2
  i_3 = 0
  j_3 = 3
  while i_0 < matrix.row_count
    while j_3 < matrix.column_count
      diagonals << [matrix[i_0,j_0], matrix[i_1, j_1], matrix[i_2, j_2], matrix[i_3, j_3]]
      j_0 += 1
      j_1 += 1
      j_2 += 1
      j_3 += 1
    end
    j_0 = 0
    j_1 = 1
    j_2 = 2
    j_3 = 3
    i_0 += 1
    i_1 += 1
    i_2 += 1
    i_3 += 1
  end
  diagonals
end

def max_consecutive_product(matrix)
  consecutives = right_diagonal_consecutive(matrix) + left_diagonal_consecutive(matrix) + matrix_horizontal_consecutive(matrix) + matrix_vertical_consecutive(matrix)
  products = []
  consecutives.each do |list|
    products << list.inject(:*)
  end
  products.max
end

matrix = Matrix.rows([[3,4,6,8,1],
                      [5,6,3,1,7],
                      [1,4,2,8,4],
                      [7,3,2,6,3],
                      [3,5,6,2,9]])

matrix = Matrix.rows([[ 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]])

puts max_consecutive_product(matrix)