Check if the String Numeric or Alphabetic

Code

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

int is_mixed(int i, int j, int k) {
    int sum = i + j + k;
    return sum >= 2;   // return 1 if two or three categories are present
}

void classify_string(const char *str) {
    int numeric = 0;
    int alpha = 0;
    int symbol = 0;

    while (*str) {
        if (*str >= 'a' && *str <= 'z' || *str >= 'A' && *str <= 'Z')
            alpha = 1;
        else if (*str >= '0' && *str <= '9')
            numeric = 1;
        else 
            symbol = 1;
        str++;
    }

    if (is_mixed(numeric, alpha, symbol)) printf("MIXED\n");
    else {
        if (numeric) printf("NUMERIC\n");
        else printf("ALPHABETIC\n");
    }
}

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