C++大写转小写多种方法详解

#include <algorithm>
#include <string>
#include <cctype>  // tolower

std::string str = "HELLO WORLD";
std::transform(str.begin(), str.end(), str.begin(),
               [](unsigned char c) { return std::tolower(c); });
// 结果: "hello world"

std::string str = "EXAMPLE TEXT";
for (auto& c : str) {
    if (std::isupper(c)) {
        c = std::tolower(c);
    }
}
// 结果: "example text"

char str[] = "UPPERCASE STRING";
for (int i = 0; str[i] != '\0'; ++i) {
    str[i] = std::tolower(static_cast<unsigned char>(str[i]));
}
// 结果: "uppercase string"

char str[] = "HELLO";
_strlwr(str); // Windows 特有，转为小写