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 val = 0;
    while(*str != '\0') {
         char ch = *str;
         int digit ;
         if(ch>='0' && ch <='9') {
            digit = ch - '0';
         } else if(ch >= 'A' && ch<= 'F') {
            digit = ch - 'A' +10;
         }  else if(ch >= 'a' && ch<= 'f') {
            digit = ch - 'a' +10;
         }


        val = val * 16 + digit;

        str++;
    }
    return val;
}

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

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

Solving Approach