# Project Euler Problem 4 in F#

Project Euler problem number 4 asks the following:

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.

Find the largest palindrome made from the product of two 3-digit numbers.

Here follows my solution:

A few considerations:

• I first define a general recursive function to determine whether a given string is a palindrome.

I basically check the first and last characters of the string; if they are the same I continue with the second and second last, and so on until I either found a pair of chars that do not match or there's only one char or none left.

Alternatively, I could have reversed the string and compared the original and reversed strings for equality; however that would have been not just more work than actually needed by the algorithm, but less useful as an excercise in learning F#.

• The actual algorithm uses brute force to test for palindromicity (neologism?) all the numbers that can be composed multiplying together 3 digits numbers (those from 100 to 999), picking the highest one. Again, as in a previous problem, I am using comprehension to generate a list of candidates.

Updated: