class PrimeMultiplication - prime-multiplication-1.0 Documentation

calculate_multiplication_table() click to toggle source

calculate the Multiplication matrix for the prime numbers Time complexity for this method is O(n^2)

# File lib/PrimeMultiplication.rb, line 78
def self.calculate_multiplication_table
      @@prime_array.each_with_index do |element1, index1|
              @@output_array[index1] = []
              @@prime_array.each_with_index do |element2, index2|
                     if(index1 == 0 && index2 == 0)
                             @@output_array[index1][index2] = element1
                     elsif (index1 == 0)
                             @@output_array[index1][index2] = element2
                     elsif (index2 == 0)
                             @@output_array[index1][index2] = element1
                     else
                              @@output_array[index1][index2] = element2*element1
                      end
              end
      end
      return @@output_array
end

get_primes() click to toggle source

Get first n prime numbers Time complexity for this method is O(n√n)

# File lib/PrimeMultiplication.rb, line 62
def self.get_primes
      @@prime_array = [""]
              @@output_array = []
  n = 2
  loop do
          if is_prime?(n)
              @@prime_array << n
      end
      n = n + 1
      break if @@prime_array.length == @@no_of_primes+1
      end
      return @@prime_array
end

get_user_input() click to toggle source

Get the number of primes user wants

# File lib/PrimeMultiplication.rb, line 19
    def self.get_user_input
            input_right = false
            @@no_of_primes = 0
            loop do
                    print "Enter the number of primes you want: "
                    @@no_of_primes = gets.chomp.to_i
                    input_right = (@@no_of_primes.to_i > 0) ? true : false
                    if @@no_of_primes <= 0
                            print "\n Please enter a number( > 0 ) \n"
                            @@no_of_primes = 0
                    end
                    break if input_right
            end
@@no_of_primes = @@no_of_primes
    end

get_user_input_for_test() click to toggle source

Same as get_user_input but for TDD to check if the program takes any other input other than a positive number

# File lib/PrimeMultiplication.rb, line 36
def self.get_user_input_for_test
        @@no_of_primes = 0
        print "\n \t Enter value for the number of primes you want: "
        @@no_of_primes = gets.chomp.to_i
        if @@no_of_primes <= 0
                print "Please enter a number( > 0 ): "
                @@no_of_primes = 0
                return
        end
        @@no_of_primes = @@no_of_primes
end

is_prime?(number) click to toggle source

Check if a number is prime Time complexity of this method is O(√n)

# File lib/PrimeMultiplication.rb, line 50
def self.is_prime?(number)
        return false if number == 1
        (2..(Math.sqrt(number).to_i)).each do |i|
                if number % i == 0
                        return false
                end
        end
        true
end

ordinal(number) click to toggle source

helper method to give ordinal of a number eg. 1 should return 1st, 2 should return 2nd etc.

# File lib/PrimeMultiplication.rb, line 136
def self.ordinal(number)
      ending =
    case number % 100
      when 11, 12, 13 then 'th'
      else
        case number % 10
          when 1 then 'st'
          when 2 then 'nd'
          when 3 then 'rd'
          else 'th'
          end
      end
              return number.to_s + ending
end

print_prime_multiples() click to toggle source

print the Multiplication table on to the console Time complexity for this function is O(n^2)

# File lib/PrimeMultiplication.rb, line 98
def self.print_prime_multiples
      tabs = "\t" * (@@no_of_primes/2 - 3) rescue "\t"
  print "\n #{tabs} Multiplication Table for first #{@@no_of_primes} Prime numbers \n\n"

  @@prime_array.length.times do |i|
              print " _  _  _"
      end
      print "\n"

      @@prime_array.length.times do |i|
              if(i == 0)
                      print "| \t"
              else
                      print "| #{ordinal(i)} \t"
              end
      end
      print "|\n"
      
      @@prime_array.length.times do |i|
              print " _  _  _"
      end
      print "\n"
      
      @@output_array.each do |i|
    print "\n"
              i.each do |j|
                      print "| #{j} \t"
              end
              print "|\n"
              i.each do |j|
                      print " _  _  _"
              end
              print "\n"
      end
      return
end

run() click to toggle source

Get the program up and running by calling the functions in order

# File lib/PrimeMultiplication.rb, line 11
    def self.run
            get_user_input
            get_primes
calculate_multiplication_table
print_prime_multiples
    end