std::string str = "STriNg oF mIxID CasE lETteRS"

C + 11 +

使用for_each std:: for_each (str.begin (), str.end (), [] (char & c) {c =: toupper (c);})； 使用转换 std::变换(str.begin (), str.end (), str.begin ():: toupper);

c++(仅限windows)

_strupr_s(str, str.length());

c++(使用Boost库)

boost::to_upper_copy(str)

不确定是否有内置功能。试试这个:

包括ctype.h或cctype库，以及stdlib.h作为预处理器指令的一部分。

string StringToUpper(string strToConvert)
{//change each element of the string to upper case
   for(unsigned int i=0;i<strToConvert.length();i++)
   {
      strToConvert[i] = toupper(strToConvert[i]);
   }
   return strToConvert;//return the converted string
}

string StringToLower(string strToConvert)
{//change each element of the string to lower case
   for(unsigned int i=0;i<strToConvert.length();i++)
   {
      strToConvert[i] = tolower(strToConvert[i]);
   }
   return strToConvert;//return the converted string
}

不使用任何库:

std::string YourClass::Uppercase(const std::string & Text)
{
    std::string UppperCaseString;
    UppperCaseString.reserve(Text.size());
    for (std::string::const_iterator it=Text.begin(); it<Text.end(); ++it)
    {
        UppperCaseString.push_back(((0x60 < *it) && (*it < 0x7B)) ? (*it - static_cast<char>(0x20)) : *it);
    }
    return UppperCaseString;
}

我的解决方案(清除第6位):

#include <ctype.h>

inline void toupper(char* str)
{
    while (str[i]) {
        if (islower(str[i]))
            str[i] &= ~32; // Clear bit 6 as it is what differs (32) between Upper and Lowercases
        i++;
    }
}

下面的方法对我有用。

#include <algorithm>
void  toUpperCase(std::string& str)
{
    std::transform(str.begin(), str.end(), str.begin(), ::toupper);
}

int main()
{
   std::string str = "hello";
   toUpperCase(&str);
}

//works for ASCII -- no clear advantage over what is already posted...

std::string toupper(const std::string & s)
{
    std::string ret(s.size(), char());
    for(unsigned int i = 0; i < s.size(); ++i)
        ret[i] = (s[i] <= 'z' && s[i] >= 'a') ? s[i]-('a'-'A') : s[i];
    return ret;
}