Rob On Rails

Just finished Project 4.

This isn’t the most concice code, because i functionised it, but it works quite well.

class Numeric
	def is_palindrome?
		s_num = self.to_s
		half = s_num[0..(s_num.length/2)-1].to_s
		s_num == half + half.reverse or
			(s_num.length%2 == 1 and s_num == half + s_num[s_num.length/2,1].to_s + half.reverse)
	end
end


def find_largest_palindrome number_digits

	highest_number = (9.to_s * number_digits).to_i
	lowest_number = (1.to_s + 0.to_s* (number_digits - 1)).to_i
	
	largest = 0
	largest_sqrt = 0

	highest_number.downto(lowest_number).each do |num1|
		highest_number.downto(num1).each do |num2|
			if largest_sqrt * 2 > num1 + num2
				break
			end
		
			if (num1 * num2).is_palindrome? and num1 * num2 > largest
				largest = num1 * num2
				largest_sqrt = Math.sqrt(largest)
			end
		end		
	end
	largest
end

puts "Largest palendrome is #{find_largest_palindrome 3}"