Convert Hexadecimal String to Integer Without strtol or sscanf functions

Code

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

uint16_t hex_to_uint(const char *str) {
    uint16_t value = 0;
    for (int i = 0; str[i] != '\0'; i = i + 1) {
        uint16_t digit = 0;
        if (str[i] >= '0' && str[i] <= '9') digit = str[i] - '0';
        else if (str[i] >= 'a' && str[i] <= 'f') digit = str[i] - 'a' + 0xA;
        else if (str[i] >= 'A' && str[i] <= 'F') digit = str[i] - 'A' + 0xA;
        value = (value << 4) | digit;
    }
    return value;
}

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

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

Solving Approach