Select Array Items Containing Elements From Other Array, Allow Partial Match

Question

Let's say I have a program like this:

class Student
  attr_reader :first_name, :last_name, :subject, :color

  def initialize(first_name, last_name, subject, color)
    @first_name = first_name
    @last_name = last_name
    @subject = subject
    @color = color
  end

  def keywords
    [] << @first_name << @last_name << @subject << @color
  end
end

student1 = Student.new('john', 'smith', 'math', 'blue')
student2 = Student.new('ann', 'smitten', 'english', 'blue')
students = [student1, student2]

students.select do |student|
   ...
end

I'm trying to accomplish the following:

1) select an array of Students that match my query with my Student.keywords array

2) my query is also an array of single words

3) if queryeven partially matches keyword it's a "match"

For example keywords for student1 are: ['john', 'smith', 'math', 'blue']

any of the following query arrays IS A MATCH

['j', 'mat'], ['it', 'blue', 'green']

any of the following query arrays IS NOT A MATCH

['johny'], ['johny', 'smithy', 'mathy', 'bluegreen']

How would I write this? I've been scratching my head for hours and no joy!

Also, I do need this to be fairly performant since I may need to iterate over 1000 or more array elements. I need a pure ruby solution as well.

['it', 'blue', 'green'] is not a match, because no students have green. — Sergio Tulentsev
– Sergio Tulentsev, Commented Sep 8, 2016 at 7:58
Here's code: pastebin.com/5X4WwmJL. The core of it is the .grep(Regexp.new(keyword)) part. It filters array, leaving only those elements which contain the keyword. — Sergio Tulentsev
– Sergio Tulentsev, Commented Sep 8, 2016 at 8:00
if any of the words or partial words match it is a match, so ['it', 'blue', 'green'] is a match — Leo Net
– Leo Net, Commented Sep 8, 2016 at 8:05
Yeah!!! This works like a charm with .any? and downcasing my search and keyword arrays! Can you post the code as an answer so I can mark it. Thank you! — Leo Net
– Leo Net, Commented Sep 8, 2016 at 17:34

Sergio Tulentsev · Accepted Answer · 2016-09-09 07:09:45Z

Here's working code. Plain ruby and all. The core of it is the .grep(Regexp.new(keyword)) part. It filters array, leaving only those elements which contain the keyword.

class Student
  attr_reader :first_name, :last_name, :subject, :color

  def initialize(first_name, last_name, subject, color)
    @first_name = first_name
    @last_name = last_name
    @subject = subject
    @color = color
  end

  def keywords
    [ first_name, last_name, subject, color ]
  end
end

class Matcher
  attr_reader :student, :search_keywords

  def initialize(student, search_keywords)
    @student = student
    @search_keywords = search_keywords
  end

  def match?
    search_keywords.any? do |kw|
      student.keywords.grep(Regexp.new(kw)).length > 0
    end
  end
end

def count_results(students, query)
  students.select {|s| Matcher.new(s, query).match? }.length
end

student1 = Student.new('john', 'smith', 'math', 'blue')
student2 = Student.new('ann', 'smitten', 'english', 'blue')
students = [student1, student2]

count_results(students, ['j', 'mat']) # => 1
count_results(students, ['it', 'blue', 'green']) # => 2
count_results(students, ['johny']) # => 0
count_results(students, ['johny', 'smithy', 'mathy', 'bluegreen']) # => 0

SteveTurczyn · Accepted Answer · 2016-09-08 08:15:20Z

So basically as long as at least one element matches, it's a match?

def match(search_array, student_array)
  # initialize output array
  matching_students = [] 
  # iterate through all students
  student_array.each do |student|
    # this student not yet matching
    matched_student = false
    # iterate through student's keywords
    student.keywords.each do |keyword|
      # iterate through search words
      search_array.each do |word|
        # test for match
        if keyword.start_with? word
          # add to array
          matching_students << student
          # flag current student as matched
          matched_student = true
        end
        # don't continue with search array if student already matched
        break if matched_student
      end
      # don't continue with student.keywords if student already matched
      break if matched_student
    end
  end
  matching_students
end

This is fairly preformant because not all search terms and keywords are examined once it's determined that the student is a match.

Michael Kohl · Accepted Answer · 2016-09-08 08:02:57Z

Not the most efficient, but straight-forward and does what you want:

class Student
  attr_reader :first_name, :last_name, :subject, :color

  def initialize(first_name, last_name, subject, color)
    @first_name = first_name
    @last_name = last_name
    @subject = subject
    @color = color
  end

  def keywords
    [first_name, last_name, subject, color]
  end

  def matches_search?(search_terms)
    search_terms.any? { |search_term| keywords.find { |kw| kw.match(search_term) } }
  end
end

student1 = Student.new('john', 'smith', 'math', 'blue')
student2 = Student.new('ann', 'smitten', 'english', 'blue')
students = [student1, student2]

should_match = [['j', 'mat'], ['it', 'blue', 'green']]
should_not_match = ['johny'], ['johny', 'smithy', 'mathy', 'bluegreen']

should_match.map { |search| students.select { |student| student.matches_search?(search) } }
# returns an array of 2 times student one

should_not_match.map { |search| students.select { |student| student.matches_search?(search) } }
# two empty arrays, i.e. no student matched

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