Question

I’m NOT asking for a solution to this riddle.

So, I’m working through the Project Euler problems using Ruby.

I made a palindrome checker with the following method:

def is_palindrome(n)
  if n.to_s == n.to_s.reverse
      true
  else
      false
  end
end

Using this, I use the next method to try and find the largest palindrome made with two 3 digit numbers.

x = 999
y = 998

while y > 100
  if is_palindrome(x * y) == true
    puts (x * y)
  else
    x-=1
    y-=1
  end
end

The result is the terminal throws a complete fit and gets stuck on 289982 and has to be Ctrl+C’d for it to stop.

As I said, I’m not looking for a solution to this riddle, but I want to know what it is my code is doing for this to happen. I’m still learning so my code is likely to be rather ugly, so extra karma points to anyone that can help me out with this.

Answer 1

In case a palindrome is found, you don’t decrement your variables. Since the variables remain the same, the same palindrome is found again. And so it goes…