C++ 字符串大小写转换 - 将所有小写字母转换为大写字母

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

int main() {
    std::string str;
    std::getline(std::cin, str);

    for (int i = 0; i < str.length(); i++) {
        if (std::islower(str[i])) {
            str[i] = std::toupper(str[i]);
        }
    }

    std::cout << str << std::endl;

    return 0;
}