Solution to problem 55 in Julia

src/Julia/Problem055.jl

@@ -0,0 +1,73 @@
+#=
+Created on 03 Oct 2021
+
+@author: David Doblas Jiménez
+@email: daviddoji@pm.me
+
+Solution for Problem 55 of Project Euler
+https://projecteuler.net/problem=55
+=#
+
+using BenchmarkTools
+
+function is_palindrome(num)
+    return num == reverse(num)
+end
+
+function Problem55()
+    #=
+    If we take 47, reverse and add, 47 + 74 = 121, which is palindromic.
+
+    Not all numbers produce palindromes so quickly. For example,
+
+        349 + 943 = 1292,
+        1292 + 2921 = 4213
+        4213 + 3124 = 7337
+
+    That is, 349 took three iterations to arrive at a palindrome.
+
+    Although no one has proved it yet, it is thought that some numbers, like 196,
+    never produce a palindrome. A number that never forms a palindrome through the
+    reverse and add process is called a Lychrel number. Due to the theoretical nature
+    of these numbers, and for the purpose of this problem, we shall assume that a
+    number is Lychrel until proven otherwise. In addition you are given that for
+    every number below ten-thousand, it will either:
+    (i) become a palindrome in less than fifty iterations, or,
+    (ii) no one, with all the computing power that exists, has managed so far to map
+    it to a palindrome.
+
+    In fact, 10677 is the first number to be shown to require over fifty iterations
+    before producing a palindrome:
+
+        4668731596684224866951378664 (53 iterations, 28-digits).
+
+    Surprisingly, there are palindromic numbers that are themselves Lychrel numbers;
+    the first example is 4994.
+
+    How many Lychrel numbers are there below ten-thousand?
+    =#
+
+    ans = 0
+    for n in 11:10_000
+        num = n
+        is_lychrel = true
+        for it in 0:50
+            num += parse(BigInt, reverse(string(num)))
+            if is_palindrome(digits(num, base=10))
+                is_lychrel = false
+                break
+            end
+        end
+        if is_lychrel
+            ans += 1
+        end
+    end
+
+    return ans
+end
+
+
+println("Time to evaluate Problem 55:")
+@btime Problem55()
+println("")
+println("Result for Problem 55: ", Problem55())