設問
Description:
Write a program to determine the biggest prime palindrome under 1000.
Input sample:
None
Output sample:
Your program should print the largest palindrome on stdout. i.e.
929
やってみた
#!/usr/bin/env ruby def prime? num half_num = num / 2 (2..half_num).each do |n| return false if num % n == 0 end true end def halv str half_size = str.size / 2 first = str[0, half_size] last = str[-half_size, half_size] [first, last] end def palindrome? num first, last = halv(num.to_s) first == last.reverse end 1000.downto(2) do |n| if (prime?(n) and palindrome?(n)) puts n break end end