Class: PrimeMultiplication

Inherits:
Object
  • Object
show all
Defined in:
lib/PrimeMultiplication.rb

Overview

Time complexity for this program is O(n^2)

Class Method Summary collapse

Class Method Details

.calculate_multiplication_table ⇒ Object

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



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# 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 ⇒ Object

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



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# 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 ⇒ Object

Get the number of primes user wants



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# 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 ⇒ Object

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



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# 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) ⇒ Boolean

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

Returns:

  • (Boolean) 


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# 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) ⇒ Object

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



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# 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 ⇒ Object

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



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# 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 ⇒ Object

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



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# File 'lib/PrimeMultiplication.rb', line 11

def self.run
	get_user_input
	get_primes
   calculate_multiplication_table
   print_prime_multiples
end