p018-maxpathsum.rb

data=[[75],
[95, 64],
[17, 47, 82],
[18, 35, 87, 10],
[20,  4, 82, 47, 65],
[19,  1, 23, 75,  3, 34],
[88,  2, 77, 73,  7, 63, 67],
[99, 65,  4, 28,  6, 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,  4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31],
[4,  62, 98, 27, 23,  9, 70, 98, 73, 93, 38, 53, 60,  4, 23]]
data.each_index { |i|
  if i==0 ; next end
  data[i].each_index { |j|
    if j==0 
      data[i][j]+=data[i-1][j]
    elsif j==(data[i].length-1) 
      data[i][j]+=data[i-1][j-1]
    else
      data[i][j]+=[data[i-1][j-1],data[i-1][j]].max
    end
  }
}
print data[data.length-1].max