Converting from Binary to Decimal without using arithmetic operations

Question

I had this written until i realized * is an arithmetic operation.

I want to return a nonnegative integer representation of the binary sequence input. IE. 0x4a returns 74 in decimal

typedef unsigned bit16;

unsigned int bin_to_dec(bit16 x)
{
int dec=0;
int k=0;
int remainder;

while (x!= 0){
    remainder = x%10;
    dec+=remainder*k;
    k=k+2;
    x=x/10;
}

:(

How would I go about this conversion if I can't use arithmetic operations other than +/-?

Answer 1

As + and - are allowed...Instead of multiplying into k*reamainder try looping this way

int n;//consider new int

In the while loop write first line as

n=remainder;

Instead of *

for(i=0;i<k;i++)
    remainder+=n;

This would do the multiplication :).

And for x%10, construct a function

int mod(int n)
{
   int m;
   while(n>0)
   {
      n=n-10;
      m=n;
    }
   return m;
}

And for x/10 it'd be the same but you must return number of times you subtracted like this :

int mod(int n)
{
   int count=0;
   while(n>0)
   {
      count=count+1;
      n=n-10;
   }
   return count;
}

edit : If + and - are also not allowed try making functions for them using binary operators and use them instead of + and - in the above answer!