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
    int n,k=0,i,num=0;
    for(n=0;str[n]!='\0';n++);
    i=n-1;
    while(i>=0)
    {
        if(str[i]>='0'&&str[i]<='9')
        {
            num|=str[i]-'0'<<k;
        }
        else if(str[i]>='A'&&str[i]<='F')
        {
              num|=((str[i]-'A')+10)<<k;
        }
        else if(str[i]>='a'&&str[i]<='f')
        {
              num|=((str[i]-'a')+10)<<k;
        }

        
        k=k+4;
        i--;
    }
    return num;
}

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

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

Solving Approach