How can I generate random uppercase letters in C?

[leo255]

Hello,

Below is what I tried. I can only use getchar/putchar for IO. How would I go about randomly generating 40 uppercase letters? I know that uppercase letters are 65 - 90 on the ASCII table, just not sure how to execute this properly.

Thanks.

void getRandomStr(){

    char str[40];
    int i;

    for (i = 0; i < 40; i++){

    char c = rand() % 26;

    str[i] = c;

 }

}

[giblit]

Try char c = 'A' + rand() % 26; or str[i] = 'A' + c; or if you really want you can simply add 65 which would be the same as adding 'A'[/code]

[leo255]

^^Thanks! I actually figured it out:

void getRandomStr(){


    char str[40];
    int i;

    for (i = 0; i < 40; i++){

        char c = (90 - (rand() % 26));

        str[i] = c;

    }

    for (i = 0; i < 40; i++){

putchar(str[i]);

    }

}

Just need to see how I can replace the printf() with putchar(). Working on it now.

Edit: guess you just replace the printf() with putchar(str[i]); Seemed easy enough.

[giblit]

Seems a bit obfuscated doing it that way or even char c = 'Z' - rand() % 26; which is equivalent to what you are doing. Most people would start from the first letter and add on to it instead of starting from the back and counting down.

[leo255]

I'm wondering why it's generating the same letters every time. The letters below are generated via online compilers, as well.

MDOIYYNJYSXWZIALDPPBSRWWJHXWCIQNLDUICHQB

[giblit]

How are you seeding it? I would suggest: srand(time(NULL));