Greplin solution

gistfile1.rb

require 'prime'
require 'net/http'

puts "1: " + Net::HTTP.get(URI.parse('http://challenge.greplin.com/static/gettysburg.txt')).tap {|str|
  break (0...str.size).flat_map {|i|
    (i..str.size).inject([]) {|r, j|
      str[i..j].tap {|chunk|
        break chunk == chunk.reverse ? r << chunk : r
      }
    }
  }.max_by(&:length)
}

puts "2: " + Prime.prime_division(Enumerator.new {|x|
  a, b = 1, 1
  loop {
    a, b = b, a + b
    x << b
  }
}.each {|x|
  break x if x > 227_000 and x.prime?
} + 1).map(&:first).inject(:+).to_s

puts "3: " + Net::HTTP.get(URI.parse('http://challenge.greplin.com/static/numbers.csv')).strip.split(/,\s*/).map(&:to_i).tap {|set|
  break (2..set.size).inject(0) {|c, n|
    set.combination(n).inject(c) {|i, x|
      x[0..-2].inject(:+) == x[-1] ? i + 1 : i
    }
  }
}.to_s