c++ n in regex

C++: Using the 'n' in Regex

To use the 'n' in regular expressions in C++, you can use it to match the preceding character n times, where n is a non-negative integer. Here's how you can use the 'n' in regex in C++:

1. Include the Necessary Header File: Include the header file at the beginning of your C++ program to use regular expressions.

2. Create a Regular Expression Pattern: Define a regular expression pattern using std::regex, for example: std::regex pattern("ab{n}").

3. Match the Pattern: Use std::regex_match or std::regex_search to match the pattern against the input string.

4. Replace the Pattern: Use std::regex_replace to replace the matched pattern with a specified string.

5. Access Matched Substrings: Access the matched substrings using std::smatch or std::cmatch for capturing groups.

Here's an example of using the 'n' in regex to match the preceding character 'a' 3 times:

#include <iostream>
#include <regex>

int main() {
    std::string input = "abbb";
    std::regex pattern("ab{3}");
    if (std::regex_match(input, pattern)) {
        std::cout << "Pattern matched!" << std::endl;
    }
    return 0;
}