如何在C++中解析字符串

#include<iostream>
#include<string>

int main() {
    std::string str = "Hello, world!";
    std::string sub_str = str.substr(0, 5);
    std::cout << "The first 5 characters of the string are: "<< sub_str<< std::endl;
    return 0;
}

#include<iostream>
#include <sstream>
#include<vector>

int main() {
    std::string str = "1 2 3 4 5";
    std::stringstream ss(str);
    std::vector<int> numbers;
    int num;
    while (ss >> num) {
        numbers.push_back(num);
    }
    for (int i = 0; i< numbers.size(); ++i) {
        std::cout<< numbers[i] << " ";
    }
    std::cout<< std::endl;
    return 0;
}

#include<iostream>
#include<string>
#include<vector>

int main() {
    std::string str = "Hello, world!\nThis is a test.";
    std::stringstream ss(str);
    std::vector<std::string> lines;
    std::string line;
    while (std::getline(ss, line)) {
        lines.push_back(line);
    }
    for (int i = 0; i< lines.size(); ++i) {
        std::cout<< lines[i]<< std::endl;
    }
    return 0;
}