在C＃中比较两个字符串

Question

I have a program that needs to compare any given string with a predefined string and determine if an insertion error, deletion error, transposition or substitution error was made.

For example, if the word dog was presented to the user and the user submits dogs or doge , it should notify the user that an insertion error has been made.

How do I go about this?

Answer 1

You probably need to write a method for each of the individual error types to see if it's an error, like:

bool IsInsertionError(string expected, string actual) {
    // Maybe look at all of the chars in expected, to see if all of them
    // are there in actual, in the correct order, but there's an additional one
}

bool IsDeletionError(string expected, string actual) {
    // Do the reverse of IsInsertionError - see if all the letters
    // of actual are in expected, in the correct order,
    // but there's an additional one
}

bool IsTransposition(string expected, string actual) {
    // This one might be a little tricker - maybe loop through all the chars,
    // and if expected[i] != actual[i], check to see if 
    // expected[i+1] = actual[i] and actual[i-1]=expected[i]
    // or something like that
}

Once you build out all the individual rules, and you first check for regular equality, fire each of them off one at a time.

You've got to just break problems like this down into small components, then once you have a bunch of easy problems, solve them one at a time.

Answer 2

Off the top of my head but I think this should get you started:

Insertion and Deletion should be pretty simple; just check the lengths of the strings.

if(originalString.Length > newString.Length) 
{
    //deletion
}
else if(originalString.Length < newString.Length)
{
    //insertion
}

To detect transposition , check if the lengths match and if so, you could create two List<char> from the two strings. Then check if they match using the expression below

bool isTransposed = originalList.OrderBy(x => x).SequenceEquals(newList.OrderBy(y => y));

To detect substitution , you could use the Hamming Distance and check if it's greater than 0.

Answer 3

I would suggest you to create a function which will take a parameter as the input sting . The function would look more or less like this. Use the function wherever you want then.

private void CheckString(string userString)
{
    string predefinedString = "dog";
    if (userString == predefinedString)
    {
        // write your logic here
    }
    else
    {
        MessageBox.Show("Incorrect word"); // notify the users about incorrect word over here
    }
}