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 result = 0;
    int i = 0;

    while (str[i] != '\0')
    {
        char c = str[i];
        uint8_t value;

        if (c >= '0' && c <= '9')
        {
            value = c - '0';
        }
        else if (c >= 'A' && c <= 'F')
        {
            value = c - 'A' + 10;
        }
        else if (c >= 'a' && c <= 'f')
        {
            value = c - 'a' + 10;
        }
        else
        {
            return 0;
        }

        result = result * 16 + value;
        i++;
    }

    return result;
}

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

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

Solving Approach