C++如何实现正则匹配 C++正则表达式的基本用法与示例

#include <iostream>
#include <regex>
#include <string>

bool isValidEmail(const std::string& email) {
    const std::regex pattern("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$");
    return std::regex_match(email, pattern);
}

int main() {
    std::string email1 = "test@example.com";
    std::string email2 = "invalid-email";

    std::cout << email1 << ": " << (isValidEmail(email1) ? "Valid" : "Invalid") << std::endl;
    std::cout << email2 << ": " << (isValidEmail(email2) ? "Valid" : "Invalid") << std::endl;

    return 0;
}

#include <iostream>
#include <regex>
#include <string>

int main() {
    std::string text = "Contact us at 123-456-7890 or 098-765-4321.";
    std::regex phone_regex("\d{3}-\d{3}-\d{4}");
    std::smatch match;

    std::cout << "Phone numbers found:" << std::endl;
    std::string::const_iterator searchStart( text.cbegin() );
    while ( std::regex_search( searchStart, text.cend(), match, phone_regex ) )
    {
        std::cout << match[0] << std::endl;
        searchStart = match.suffix().first;
    }

    return 0;
}

#include <iostream>
#include <regex>
#include <string>
#include <chrono>

int main() {
    std::string text = "This is a test string with some numbers: 123, 456, 789.";
    std::regex number_regex("\d+"); // 匹配一个或多个数字

    // 预编译正则表达式
    auto start = std::chrono::high_resolution_clock::now();
    for (int i = 0; i < 10000; ++i) {
        std::smatch match;
        std::string::const_iterator searchStart( text.cbegin() );
        while ( std::regex_search( searchStart, text.cend(), match, number_regex ) )
        {
            searchStart = match.suffix().first;
        }
    }
    auto end = std::chrono::high_resolution_clock::now();
    auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);

    std::cout << "Time taken with precompiled regex: " << duration.count() << " milliseconds" << std::endl;

    return 0;
}