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) {
    // Your logic here
    uint16_t res = 0;
    uint8_t value;

    while (*str != '\0')
    {
        if (*str >= '0' && *str <= '9')
            value = *str - '0';
        else if (*str >= 'a' && *str <= 'f')
            value = *str - 'a' + 10;
        else if (*str >= 'A' && *str <= 'F')
            value = *str - 'A' + 10;
        else
            break; // hoặc return error

        res = (res << 4) | value;
        str++;
    }

    return res;
}

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

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