c++ - uppercase to lowercase and vice versa

Question

this code should convert uppercase to lowercase and vice versa .. the problem is its returning both upper and lower .. for example when i enter the word "tuna" it returns "TUNAtuna" .. help please

string rev_letter(string s)
{
    string word = s;
    string final_word="";
    char c;
    for(int i = 0 ; i<=(word.length()-1);i++)
    {
    c=word.at(i);
    if(isupper(c))
    {
        putchar(tolower(c));
        final_word+=c;
    }
    else
    {
        putchar(toupper(c));
        final_word+=c;
    }

    }
    return final_word;
} 

Answer 1

当您使用 时putchar，您会按预期打印字符（到屏幕上），但不会将字符放入final_word. 在 final_word 中，您实际上放置了初始单词。

尝试这个：

string rev_letter(string s)
{
    string word = s;
    string final_word="";
    char c;
    for(int i = 0 ; i<(word.length());i++)
    {
       c=word.at(i);
       if(isupper(c))
       {
           final_word+=tolower(c);
       }
       else
       {
           final_word+=toupper(c);
       }
    }

    return final_word;
}