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 val = 0;
    for (int i=0; str[i]; i++) {
        if (str[i] >= '0' && str[i] <= '9')
            val = (val << 4) | (str[i] - '0');
        else if (str[i] >= 'A' && str[i] <= 'Z')
            val = (val << 4) | (str[i] - 'A' + 10);
        else 
            val = (val << 4) | (str[i] - 'a' + 10);
    }
    return val;
}

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

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