euler11.rb

$gridNums = %Q(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
)

def gridNum(nums)
  matrix = []
  nums.each_line do |line|
    no_ary = line.split(/\s/)
    matrix << no_ary.map{|no|no.to_i}
  end
  matrix
end

def max_cons_product(matrix,cons)
  matrix.inject(0) do |sum,row|
    ary = row.each_cons(cons).map do |con|
      con.inject(1){|pro,c| pro *= c}
    end
    sum = ary.max if not ary.empty? and ary.max > sum
    sum
  end
end

def reverse_diagonal(matrix)
  low_diag_ary,diag_ary = [],[]
  3.upto(19) do |col|
    low_diag,diag = [],[]
    0.upto(col) do |row|
      diag << matrix[row][col-row]
      low_diag << matrix[col-row][row]
    end
    diag_ary << diag
    low_diag_ary << low_diag
  end
  diag_ary + low_diag_ary
end

def diagonal(matrix)
  low_diag_ary,diag_ary = [],[]
  0.upto(16).each do |col|
    low_diag,diag = [],[]
    (0.upto(19 - col)).each do |row|
      diag << matrix[row][row+col]
      low_diag << matrix[row+col][row]
    end
    diag_ary << diag
    low_diag_ary << low_diag 
  end
  diag_ary + low_diag_ary
end

def calculate(matrix)
  rowMax = max_cons_product(matrix,4)
  colMax = max_cons_product(matrix.transpose,4)

  diag = diagonal(matrix)
  r_diag = reverse_diagonal(matrix)
  diaMax = max_cons_product(matrix,4)
  r_diaMax = max_cons_product(r_diag,4)

  [rowMax,colMax,diaMax,r_diaMax].max

end

matrix = gridNum($gridNums)
p calculate(matrix)