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;
    
    int i=0;
    while(str[i] != '\0'){
        int digit;
        if(str[i] >= '0' && str[i] <= '9'){
            digit = str[i] - '0';
        }
        else if(str[i] >= 'A' && str[i] <= 'F') {
            digit = str[i] - 'A' + 10;
        }
        else if(str[i] >= 'a' && str[i] <= 'f') {
            digit = str[i] - 'a' + 10;
        }
        i++;
        val = (val << 4 ) | digit;
       
    }
    return val;
}

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

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

Solving Approach