36 - 正则表达式

基本用法

#include <regex>

// 匹配
std::regex pattern(R"(\d{3}-\d{4})");  // 电话号码格式
std::string text = "Call 123-4567 or 890-1234";

if (std::regex_search(text, pattern)) {
    std::cout << "Found!\n";
}

// 提取匹配
std::smatch match;
if (std::regex_search(text, match, pattern)) {
    std::cout << match[0] << "\n";  // 123-4567
}

搜索所有匹配

std::string text = "123-4567, 890-1234, 567-8901";
std::regex pattern(R"(\d{3}-\d{4})");

auto begin = std::sregex_iterator(text.begin(), text.end(), pattern);
auto end = std::sregex_iterator();

for (auto it = begin; it != end; ++it) {
    std::cout << it->str() << "\n";
}

替换

std::string text = "Hello World, Hello C++";
std::regex pattern("Hello");
std::string replacement = "Hi";

std::string result = std::regex_replace(text, pattern, replacement);
// "Hi World, Hi C++"

捕获组

std::regex pattern(R"((\w+)@(\w+)\.(\w+))");
std::string email = "user@example.com";
std::smatch match;

if (std::regex_match(email, match, pattern)) {
    std::cout << "User: " << match[1] << "\n";   // user
    std::cout << "Domain: " << match[2] << "\n";  // example
    std::cout << "TLD: " << match[3] << "\n";     // com
}

regex_match vs regex_search

std::regex pattern(R"(\d+)");

// regex_match: 整个字符串必须匹配
std::regex_match("123", pattern);    // true
std::regex_match("123abc", pattern); // false

// regex_search: 部分匹配即可
std::regex_search("123abc", pattern); // true

正则表达式语法速查

语法	说明
.	任意字符
\d	数字 [0-9]
\w	单词字符 [a-zA-Z0-9_]
\s	空白字符
*	0次或多次
+	1次或多次
?	0次或1次
{n}	恰好n次
{n,m}	n到m次
^	行首
$	行尾
[]	字符类
()	捕获组
|	或

实用示例

// 验证邮箱
bool isValidEmail(const std::string& email) {
    std::regex pattern(R"(^[\w.-]+@[\w.-]+\.\w+$)");
    return std::regex_match(email, pattern);
}

// 提取数字
std::vector<int> extractNumbers(const std::string& text) {
    std::regex pattern(R"(-?\d+)");
    std::vector<int> numbers;
    auto begin = std::sregex_iterator(text.begin(), text.end(), pattern);
    for (auto it = begin; it != std::sregex_iterator(); ++it) {
        numbers.push_back(std::stoi(it->str()));
    }
    return numbers;
}

// 格式化日期
std::string formatDate(const std::string& input) {
    std::regex pattern(R"((\d{4})-(\d{2})-(\d{2}))");
    return std::regex_replace(input, pattern, "$3/$2/$1");
}

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