如何在一行上连接多个C++字符串？

#include<iostream>
#include<string>

int main() {
    std::string str1 = "Hello";
    std::string str2 = "World";
    std::string str3 = str1 + " " + str2;

    std::cout<< str3<< std::endl;

    return 0;
}

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

int main() {
    std::string str1 = "Hello";
    std::string str2 = "World";
    std::stringstream ss;
    ss<< str1 << " "<< str2;
    std::string str3 = ss.str();

    std::cout<< str3<< std::endl;

    return 0;
}