substrings.rb

def substrings(word, dictionary)
  dictionary.reduce(Hash.new(0)) do |substr_count, substr|
    idx = 0
    while idx < word.length
      if word[idx, substr.length] == substr
        substr_count[substr] += 1
        idx += substr.length
      else
        idx += 1
      end
    end
    substr_count
  end
end

dictionary = ["below","down","go","going","horn","how","howdy","it","i","low","own","part","partner","sit"]
p substrings("below", dictionary)
p substrings("Howdy partner, sit down! How's it going?", dictionary)