naive_string_search.rb

class StringSearch
    # naive string search implementation
    def search(pattern, text)
        pattern_array = pattern.split(//) 
        text_array = text.split(//)
        for i in 0 .. text_array.size - 1
            match_count = 0
            for j in 0 .. pattern_array.size - 1
                # keep incrementing match count for every matching character
                if text_array[i + j] == pattern_array[j]
                    match_count += 1
                else
                    break
                end
            end

            # we found a match since count equals pattern size
            if match_count == pattern_array.size
                return i
            end
        end

        return nil
    end
end

require "test/unit"
class StringSearchTest < Test::Unit::TestCase
    def test_search
        assert_equal "hello there!".index("lo"), StringSearch.new.search("lo", "hello there!")
        assert_equal "hello there!".index("miss!"), StringSearch.new.search("miss!", "hello there!")
    end
end