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prob18.rb
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prob18.rb
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#!/Users/spamram/.rvm/rubies/ruby-1.9.2-p180/bin/ruby
# Goal:
# Find the maximum total from top to bottom of the triangle.
class Leaf
attr_accessor :i, :j, :val, :max
def initialize(i, j, val)
@i, @j, @val = i, j, val.to_i
end
def self.max(a, b)
a.val > b.val ? a : b
end
end
def build_tree
raw = %{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}
tree = raw.split(/\n/).collect {|row| row.split(' ')}
0.upto(tree.length-1) do |i|
0.upto(tree[i].length-1) do |j|
tree[i][j] = Leaf.new(i, j, tree[i][j].to_i)
end
end
return tree
end
@tree = build_tree
def max_chain(leaf)
if leaf.i == (@tree.length-1)
return leaf.val
else
return leaf.max ||= (leaf.val + [max_chain(@tree[leaf.i+1][leaf.j]), max_chain(@tree[leaf.i+1][leaf.j+1])].max)
end
end
puts max_chain(@tree[0][0])