Modify naive search algo to allow tollerance - vb.net

Question

I'm trying to mod the following naive search function, to find sequences that are in a range of tollerance (each digit can be +/- X%).
this is where I start:
Public Shared Function searchX(ByVal haystack As Byte(), ByVal needle As Byte())
Dim M As Integer = needle.Length
Dim N As Integer = haystack.Length
For i As Integer = 0 To N - M
Dim j As Integer
For j = 0 To M - 1
If haystack(i + j) <> needle(j) Then Exit For
Next
If j = M Then
Return i
End If
Next
End Function
So, if I correctly understand how the Naive algo work, the comparation of the pattern with my array is done in the line If haystack(i + j) <> needle(j) Then Exit For.
So I change it like that:
'code deleted as asked from my team that own it
I tested it with different array and patterns, but now it look like it can ony find a sequence of "0"; What am I missing? Is my understand of this algo totally wrong?
UPDATE:
I put some data to minimal testing:
Dim haystack = New Byte() {&H0, &H1, &H2, &H3, &H4, &H5, &H6, &H7, &H8, &H9, &HA, &HB, &HC, &HD, &HE, &HF, &H1, &HF1, &HF4, &H3F, &H24, &HF4, &HF2, &HF4, &HF2, &H4F, &H2F, &H4F, &H2F, &H43, &HF2, &H4F, &H2F, &H4F, &H23, &H4F, &H23, &HF4, &HFF, &H42, &HF4, &HF3, &HF4, &H32, &HF4, &HF3, &H2F, &H4F, &H23, &HF0}
Dim haystack2 = New Byte() {&H0, &H1, &H2, &H3, &H4, &H5, &H6, &H7, &H8, &H9, &HC, &HD, &HE, &HD, &HE, &HF, &H1, &HF1, &HF4, &H3F, &H24, &HF4, &HF2, &HF4, &HF2, &H4F, &H2F, &H4F, &H2F, &H43, &HF2, &H4F, &H2F, &H4F, &H23, &H4F, &H23, &HF4, &HFF, &H42, &HF4, &HF3, &HF4, &H32, &HF4, &HF3, &H2F, &H4F, &H23, &HF0}
Dim needle = New Byte() {&HA, &HB, &HC}
Dim tollerance = 20
Using the needle A,B,C in the first haystack and tolerance=0 I should get the match at position 10, and none in the hatstack2. Then with tollerance = 20 I should find a match in both haystack at the same position 10 because the needle's values still in the 20% of tollerance.

Answer 1

See my comments on the For loops.
Private haystack As Byte() = New Byte(){&H0, &H1, &H2, &H3, &H4, &H5, &H6, &H7, &H8, &H9, &HA, &HB, &HC, &HD, &HE, &HF, &H1, &HF1, &HF4, &H3F, &H24, &HF4, &HF2, &HF4, &HF2, &H4F, &H2F, &H4F, &H2F, &H43, &HF2, &H4F, &H2F, &H4F, &H23, &H4F, &H23, &HF4, &HFF, &H42, &HF4, &HF3, &HF4, &H32, &HF4, &HF3, &H2F, &H4F, &H23, &HF0}
Private needle As Byte() = New Byte() {&HA, &HB, &HC}
Private haystack2 As Byte() = New Byte() {&H0, &H1, &H2, &H3, &H4, &H5, &H6, &H7, &H8, &H9, &HC, &HD, &HE, &HD, &HE, &HF, &H1, &HF1, &HF4, &H3F, &H24, &HF4, &HF2, &HF4, &HF2, &H4F, &H2F, &H4F, &H2F, &H43, &HF2, &H4F, &H2F, &H4F, &H23, &H4F, &H23, &HF4, &HFF, &H42, &HF4, &HF3, &HF4, &H32, &HF4, &HF3, &H2F, &H4F, &H23, &HF0}
Public Shared Function searchXWithT(ByVal haystack As Byte(), ByVal needle As Byte(), ByVal err As Byte) As Integer
Dim M As Integer = needle.Length
Dim N As Integer = haystack.Length
For i As Integer = 0 To N - M 'For i = 0 To 10
For j = 0 To M - 1 'For j = 0 To 2
If (CDbl(needle(j) - (needle(j) / 100 * err)) < CDbl(haystack(i + j))) And (CDbl(haystack(i + j)) < CDbl((needle(j) / 100 * err) + needle(j))) Then
Else
Exit For
End If
Next
If j = M Then 'M will always be 3 and j can never be more than 2
Return i 'i will never be returned
End If
Next
Return 0
End Function