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 hex = 0; 
    uint16_t num = 0;
    while (*str != '\0'){ 
        if (*str >= 'a'){ 
            hex = (*str - 'a') + 10; 
        } else if (*str >= 'A'){ 
            hex = (*str - 'A') + 10; 
        } else { 
            hex = *str - '0'; 
        }
        num = (num * 16) + hex; 
        str++; 
    }
    return num;
}

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

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

Solving Approach