How do you find the non-matching characters in a string?

To find the non-matching characters in a string, you can follow these steps:

1. First, you need to define what you mean by "non-matching". If you mean characters that do not appear more than once, then you are looking for unique characters. If you mean characters that do not match a certain condition or pattern, then you need to define that condition or pattern.

2. Once you have defined what "non-matching" means, you can use a loop to iterate over each character in the string.

3. For each character, check if it matches your condition. If it does not, then it is a non-matching character.

4. You can keep track of these non-matching characters in a separate list or string, which you can return or print out at the end.

Here is a simple Python code snippet that finds unique characters in a string:

def find_unique_chars(string):
    unique_chars = []
    for char in string:
        if string.count(char) == 1:
            unique_chars.append(char)
    return unique_chars

print(find_unique_chars("hello world"))

This will output ['h', 'e', ' ', 'w', 'r', 'd'], which are the characters that only appear once in the string "hello world".