119. Convert Hexadecimal String to Integer Without strtol or sscanf functions

#include <stdio.h>
#include <stdint.h>
uint16_t hex_to_uint(const char *str) {
    uint16_t res=0;
    while (*str != '\0'){
        res <<= 4;
        if ((*str) <= '9'){
            res += (*str)-'0';
        }
        else {
            if ((*str)>='a' && (*str)<='z'){
                res += (*str) - 'a' + 10;
            }else {
            res += (*str) - 'A' + 10;
            }
        }
        str++;
    }
    return res;
}
int main() {
    char hex[10];
    scanf("%s", hex);
    printf("%u", hex_to_uint(hex));
    return 0;
}