C++从字符串提取数字的技巧

#include <iostream>
#include <sstream>
#include <string>

int main() {
    std::string str = "123 45.6 abc 789";
    std::stringstream ss(str);
    int intVal;
    double doubleVal;
    std::string word;

    while (ss >> intVal) {
        std::cout << "整数: " << intVal << std::endl;
    }
    // 注意：上面循环会因非整数中断，可用动态判断类型方式改进
}

while (ss >> word) {
    std::stringstream converter(word);
    int num;
    if (converter >> num) {
        std::cout << "提取到数字: " << num << std::endl;
    }
}

#include <iostream>
#include <string>
#include <cctype>

int main() {
    std::string str = "abc123xyz456";
    std::string numStr;
    for (char c : str) {
        if (std::isdigit(c)) {
            numStr += c;
        } else {
            if (!numStr.empty()) {
                std::cout << "数字: " << std::stoi(numStr) << std::endl;
                numStr.clear();
            }
        }
    }
    if (!numStr.empty()) {
        std::cout << "数字: " << std::stoi(numStr) << std::endl;
    }
}

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

int main() {
    std::string str = "价格是19.9元，数量-5个，库存+100";
    std::regex numPattern(R"([-+]?\d*\.?\d+)");
    std::sregex_iterator iter(str.begin(), str.end(), numPattern);
    std::sregex_iterator end;

    for (; iter != end; ++iter) {
        std::string match = iter->str();
        // 判断是否为有效数字（避免单独的小数点）
        if (match.find_first_of("0123456789") != std::string::npos) {
            std::cout << "提取数字: " << match << std::endl;
        }
    }
}

#include <iostream>
#include <string>
#include <cctype>
#include <algorithm>

int main() {
    std::string str = "test123data456";
    auto it = str.begin();
    while (it != str.end()) {
        it = std::find_if(it, str.end(), ::isdigit);
        if (it != str.end()) {
            std::string num;
            while (it != str.end() && std::isdigit(*it)) {
                num += *it++;
            }
            std::cout << "数字: " << std::stoi(num) << std::endl;
        }
    }
}