Check if the String Numeric or Alphabetic

Code

#include <stdio.h>
#include <stdint.h>

void classify_string(const char *str) {
    // Your logic here
    int n = 0, a = 0, o = 0;
    if(*str == '\0') o = 1;
    for(; *str != '\0' && !o; str++){
        if(*str > '0'-1 && *str < '9'+1)
            n = 1;
            else if(*str > 'a'-1 && *str < 'z'+1)
                    a = 1;
                    else if(*str > 'A'-1 && *str < 'Z'+1)
                            a = 1;
                            else o = 1;
        if(a && n)
            o = 1;
    }
    if(o)
        printf("MIXED");
        else if(a) printf("ALPHABETIC");
                    else if(n) printf("NUMERIC");
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    classify_string(str);
    return 0;
}

Solving Approach