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;
    for(int i=0;str[i]!='\0';i++){
        uint8_t ch;
        res<<=4;
        if(str[i]>='0' && str[i]<='9'){
            ch = str[i]-'0';
        }
        else if(str[i]>='a' && str[i]<='f'){
            ch = str[i]-'a'+10;
        }
        else{
            ch = str[i]-'A'+10;
        }
        res|=ch;

    }
    return res;
}

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

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

Solving Approach