c++ascii

C++, most efficient way to change uppercase to lowercase and vice versa without condition branching

We have single character Chr on input. Output must be lowercase of Chr if Chr is uppercase and vice versa.

Trivial realization using if else statement:

if(Chr>='a' && Chr<='z') cout<<(unsigned char)(a-32);
else cout<<(unsigned char)(a+32);

Could you propose solution without any condition branching?

Something like Chr + 32*(<sign of>(Chr - 'a'))?

Update: I kept ASCII in mind when asked this question.

Solution

  • If your characters are using the ASCII character set you can xor with the value 32 to flip between upper and lower case.

    char switchCase(char letter)
{
    return letter ^ 32;
}