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) {
    // Your logic here
    uint16_t res = 0;
    uint8_t value;
    for (uint8_t i = 0; str[i] != '\0'; i++)
    {
        if (str[i] >= '0' && str[i] <= '9')
        {
            value = str[i] - '0';
        }else if (str[i] >= 'A' && str[i] <= 'Z')
        {
            value = 10 + (str[i] - 'A');
        }else if (str[i] >= 'a' && str[i] <= 'z')
        {
            value = 10 + (str[i] - 'a');
        }else{
            value = 0;
        }
        res = (res << 4) + value;
    }

    return res;
}

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

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

Solving Approach