‘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?
‘
‘NOTE: Wording was modified slightly on 24 April 2007 to emphasise
‘the theoretical nature of Lychrel numbers.

Option Explicit
Option Base 1
Sub Problem_055()
 
   Dim i       As Long
   Dim j       As Long
   Dim T       As Single
   Dim n       As String
   Dim n_rev   As String
   Dim num     As String
   Dim Answer  As Long
   Dim Max     As Long
   Dim Last    As Long
   Dim IsTest  As Boolean
   Dim Series(5) As String
 
   T = Timer ‘start timing
  IsTest = True
   If IsTest Then ‘to test the example cases
     Max = 5
      Last = 53
      Series(1) = “47”
      Series(2) = “196”   ‘Lychrel
     Series(3) = “349”
      Series(4) = “4994”   ‘Lychrel
     Series(5) = “10677”
   Else
      Max = 9999    ‘ less than 10,000
     Last = 50
  end if
 
 For j = 1 To Max
      If IsTest Then
         n = Series(j)
      Else
         n = CStr(j)
      End If
      For i = 1 To last ‘to test 10677
        n_rev = StrReverse(n)
         num = AddAsStrings(n, n_rev)
         If num = StrReverse(num) Then ‘not a Lychrel number
           Exit For
         End If
         n = num
         If i = last Then
            Answer = Answer + 1
         End If
      Next i
  Next j
 
   Debug.Print Answer; ”  Time:”; Timer – T
 
End Sub