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

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

uint16_t hex_to_uint(const char *s) {
    uint16_t r = 0;
    for (int i = 0; i < 4 && s[i] ; i++) {
        char c = s[i];
        int v = (c >= '0' && c <= '9') ? c - '0' :
                (c >= 'A' && c <= 'F') ? c - 'A' + 10 :
                (c >= 'a' && c <= 'f') ? c - 'a' + 10 : 
                0;
        r = (r << 4) | v;
    }
    return r;
}

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

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