Convert Hexadecimal String to Integer Without strtol or sscanf functions

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

uint16_t hex_to_uint(const char *str) {
    // Your logic here
    int i = 0;
    uint16_t digit = 0;
    uint16_t val = 0;

    while(str[i] != '\0'){
        char c = str[i];
        if(c >= '0' && c <= '9'){
            digit = c - '0';
            val = (val << 4) | digit;
        } else if(c >= 'A' && c <= 'F'){
            digit = c - 'A' + 10;
            val = (val << 4) | digit;
        }else if(c >= 'a' && c <= 'f'){
            digit = c -'a' + 10;
            val = (val << 4) | digit;
        }else{
            return -1;
        }
        i++;
    }
    return val;
}

int main() {
    char hex[10];
    scanf("%s", hex);

    printf("%u", hex_to_uint(hex));
    return 0;
}