Project Euler - 18

18.rb

input = """
75
95 64
17 47 82
18 35 87 10
20 04 82 47 65
19 01 23 75 03 34
88 02 77 73 07 63 67
99 65 04 28 06 16 70 92
41 41 26 56 83 40 80 70 33
41 48 72 33 47 32 37 16 94 29
53 71 44 65 25 43 91 52 97 51 14
70 11 33 28 77 73 17 78 39 68 17 57
91 71 52 38 17 14 91 43 58 50 27 29 48
63 66 04 68 89 53 67 30 73 16 69 87 40 31
04 62 98 27 23 09 70 98 73 93 38 53 60 04 23
"""

triangle = input.split(/\n/)
	        .map(&:split)
	        .reject(&:empty?)
	        .map { |r| r.map(&:to_i) }

def reduce_row(row)
  row.length < 2 ? [] : [row[0..1].max] + reduce_row(row[1..-1])
end

result = triangle.reverse.inject do |memo, row|
  reduce_row(memo).zip(row).map { |j, k| j + k }
end

p result