C++添加到字符串(输出)

#include <iostream>
#include <string>

int main() {
    std::string str1 = "Hello";
    std::string str2 = " World!";
    std::string result = str1 + str2;
    
    std::cout << result << std::endl;
    
    return 0;
}

Hello World!

#include <iostream>
#include <string>

int main() {
    std::string str1 = "Hello";
    std::string str2 = " World!";
    
    str1.append(str2);
    
    std::cout << str1 << std::endl;
    
    return 0;
}

Hello World!

#include <iostream>
#include <cstring>

int main() {
    char str1[20] = "Hello";
    char str2[] = " World!";
    
    strcat(str1, str2);
    
    std::cout << str1 << std::endl;
    
    return 0;
}

Hello World!