C programming: How to check whether the input string contains combination of uppercase and lowercase

Question

I\'m totally newbie here. As stated above, I would like to know how to check whether the input string contains combination of uppercase and lowercase. After that print a stateme

Answer 1

Step 0: variables you need

char* str;
int   i;
char  found_lower, found_upper;

Step 1: iterate through the string

for (int i = 0; str[i] != '\0'; i++)

Step 2: detect upper and lower case characters

found_lower = found_lower || (str[i] >= 'a' && str[i] <= 'z')
found_upper = found_upper || (str[i] >= 'A' && str[i] <= 'Z')

Step 3: combine the results

mixed_case = found_lower && found_upper

Step 4 (optional) break out of the for early to save some time

if (found_lower && found_upper) break;

Full source (warning: untested):

char is_mixed(char* str) {

    int   i;
    char  found_lower = false, found_upper = false;

    for (int i = 0; str[i] != '\0'; i++) {
        found_lower = found_lower || (str[i] >= 'a' && str[i] <= 'z');
        found_upper = found_upper || (str[i] >= 'A' && str[i] <= 'Z');

        if (found_lower && found_upper) break;
    }

    return (found_lower && found_upper);

}