So, I'm having a very difficult task here. I need to analyze a certain text and find the minimum number of characters it needs to become a palindrome. The text will not have any special characters or numbers, just alphabet letters. Now, I've made some progression and have tried a lot of situations correctly, but in some situations I've gotten wrong outputs on the MINIMUM number of characters needed. I've tested the below texts:

AAABBBBCCCCC - AAABBBBCCCCCBBBBAAA ✓ 7
CCCCCBBBBAAA - AAABBBBCCCCCBBBBAAA ✓ 7
BBBBCCCCCAAA - AAABBBBCCCCCBBBBAAA ✓ 7
FASLLI - FAS-I-LLI-SAF ✓ 4
ARBEN - ARBEN-EBRA ✓ 4
ARBENA - ARBEN-EBR-A ✓ 3
ARBANA - ARBAN-ABR-A ✓ 3
ALL - ALL-A ✓ 1
ALLLL - ALLLL-A ✓ 1
BAOUB - BAOU-OA-B ✓ 2
ASDRFFF - ASDRFFF-DRSA ✓ 4
AAABBB - AAABBB-AAA / BBB-AAABBB ✓ 3
ARBENARBEN - ARBENARBEN-EBRANEBRA ✓ 9
ALLALL - ALLALL-A WRONG , outputs "4" when all there's needed is 1.
AAABBBBAAABBBBCCCCC - CCCCCBBBB-AAABBBBAAABBBBCCC WRONG, outputs 14 when all there's needed is 9 chars. In this case there should be noted that there are 2 palindromes within the text (as in substrings which may have something to do with the wrong output that I get, but I can't find what it is).

If anyone can help me with what is going wrong with the 2 cases in which the output is wrong I would appreciate it very very much. My code is below.

vb Code:
  1. Public Class Form1

  2.  
  3.     Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click

  4.  
  5.         Dim counter As Integer = 0, counter2 As Integer = 0, temp As Integer = 0

  6.         Dim Half As Integer

  7.         Dim Test As Boolean = False

  8.         RichTextBox1.Text = RichTextBox1.Text.Replace(" ", "")

  9.         RichTextBox1.Text = RichTextBox1.Text.Replace(".", "")

  10.         RichTextBox1.Text = RichTextBox1.Text.Replace(vbLf, "")

  11.  
  12.         Dim j As Integer = RichTextBox1.Text.Length

  13.  
  14.         If RichTextBox1.Text.Length Mod 2 Then

  15.             ' just for help to test MsgBox("You've put an odd no. of Chars.")

  16.             Half = Math.Floor((RichTextBox1.Text.Length - 1) / 2)

  17.  
  18.             For i = 0 To Half - 1

  19.  
  20.                 For j = RichTextBox1.Text.Length - 1 To 0 Step -1

  21.                     If i < Half Then

  22.                         If RichTextBox1.Text.Chars(i) = RichTextBox1.Text.Chars(j) Then

  23.                             MsgBox(RichTextBox1.Text.Chars(i) & RichTextBox1.Text.Chars(j))

  24.                             counter = counter + 2

  25.                         Else

  26.                             MsgBox("Same chars at respective places are " & counter)

  27.                             Test = True

  28.                             MsgBox("Test became true")

  29.                             Exit For

  30.                         End If

  31.                         i += 1

  32.                     Else

  33.                         'i += 1

  34.                     End If

  35.                     ' i = i + 1

  36.                 Next

  37.  
  38.                 If Test = True Then Exit For

  39.  
  40.             Next

  41.  
  42.         Else

  43.           ' just for help to test  MsgBox("You've put an even no. of Chars.")

  44.             Half = Math.Floor((RichTextBox1.Text.Length) / 2)

  45.             MsgBox(Half)

  46.  
  47.             For i = 0 To Half - 1

  48.  
  49.                 For j = RichTextBox1.Text.Length - 1 To Half Step -1

  50.                     If i < Half Then

  51.                         If RichTextBox1.Text.Chars(i) = RichTextBox1.Text.Chars(j) Then

  52.                             '            MsgBox(RichTextBox1.Text.Chars(i) & RichTextBox1.Text.Chars(j))

  53.                             counter = counter + 2

  54.  
  55.                         Else

  56.                             MsgBox("Same chars at respective places are " & counter)

  57.                             Test = True

  58.                             MsgBox("Test became true")

  59.                             Exit For

  60.                             '   j -= 1

  61.                         End If

  62.                         i += 1

  63.                         '   Exit For

  64.  
  65.                     End If

  66.  
  67.                 Next

  68.  
  69.                 If Test = True Then Exit For

  70.  
  71.             Next

  72.  
  73.         End If

  74.  
  75.         If counter / 2 = Half Then

  76.             MsgBox("This text is a palindrome, it doesn't need any additional character.")

  77.         Else

  78.  
  79.             '     For j = RichTextBox1.Text.Length - 1 To 1 Step -1

  80.             'If RichTextBox1.Text.Chars(j) = RichTextBox1.Text.Chars(j - 1) Then

  81.  
  82.            For i = 0 To RichTextBox1.Text.Length - 2

  83.                 If RichTextBox1.Text.Chars(i + 1) = RichTextBox1.Text.Chars(i) Then

  84.                     counter2 = counter2 + 1

  85.                     MsgBox("The no. of same straight chars atm is " & counter2)

  86.                     If temp <= counter2 Then

  87.                         temp = counter2

  88.                         MsgBox("Biggest same straight char no. is " & temp)

  89.                     End If

  90.  
  91.                     MsgBox(counter2)

  92.                 Else

  93.                     counter2 = 0

  94.                     End If

  95.  
  96.             Next

  97.             If counter2 <= temp Then

  98.                 counter2 = temp

  99.             End If

  100.             MsgBox("Temp =" & temp)

  101.  
  102.             MsgBox("This text is not a palindrome, it needs " & (RichTextBox1.Text.Length - 1 - counter - temp) & " chars to become one.")

  103.         End If

  104.         'MsgBox(counter)

  105.  
  106.     End Sub

  107.  
  108. End Class