如何比较两个字符串的准确性

Question

I'm making this useless program just to get back into programming properly and I'm struggling with comparing two strings for accuracy.

---

I basically have 2 strings: (example)

(Constant that im comparing to) str1 = "abcdefghijkl"

(Input) str2 = "abcdefghjkli"

The str2 is correct up to (and including) "h". I want to know what % of the string is correct.

This is the code I have so far:

Private Function compareString(str1 As String, str2 As String)
'Compares str2 to str1 and returns a % match
Dim strNumber As Integer
Dim percentMatch As Integer
'Dim array1(16), array2(16) As Char
'array1 = str1.ToCharArray
'array2 = str2.ToCharArray

 For x = 0 To str1.Length
    'If array1(x) = array2(x) Then
    If str1(x) = str2(x) Then
        strNumber += 1
    Else
        Exit For
    End If
 Next
 percentMatch = ((strNumber / (str1.Length - 1)) * 100)
 percentMatch = CInt(CStr(percentMatch.Substring(0,4)))
 Return percentMatch

End Function The two commented sections are the other approach I tried before coming here. The code should run as follows

compareString("abcdefghijkl", "abcdefghjkli")

strNum will get to 8.

percentMatch = ((8 / 12)*100)

*percentMatch = 75

Return 75

But, its not returning this, On the lines

If str1(x) = str2(x) Then

it returns an error, "Index was outside the bounds of the array." I understand the error, just not where I am going wrong.

If theres anymore information I can give, I'll do so as soon as I see the notification :)

Thanks in Advance,

Rinslep

Answer 1

If you consider the string

str = "ABCDE";

str.Length is 5. But if you index it with a 0 based index,

str[0] = 'A'
...
str[4] = 'E'
'str[5] throws exception (5 = str.Length)

Now in your

For x = 0 To str1.Length

If you compare with my example, when x is equal to the length of the string, you are checking str[5], which is out of the bound hence throwing the exception.

Change that line to

Dim shorterLength = IIf(str1.Length < str2.Length, str1.Length, str2.Length); 'So that you cannot go beyond the boundary
For x = 0 To (shorterLength - 1)

Cheers!!!

Answer 2

you need to check the length of given strings also you should not exceed the bound and also don't exit from loop until checking whole string:

Dim x As Integer = 0  
While x < str1.Length AndAlso x < str2.Length
    If str1(x) = str2(x) Then
        strNumber += 1
    End If
    i = i + 1
End While

Answer 3

I know this has been open for a while but I've been looking into this a little. You would have to respect the length of the strings too. Say you have two strings. ABCD and AEF . AEF is 75% the length of ABCD. Each letter in ABCD is worth 25%. And there's one letter that's correct in AEF and that's A. And as A = 25%: 75% * 25% = 0,75 * 0,25 = 0,1875 = 18,75% . String AEF is 18,75% equal to ABCD.

Hope you understood. :)