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Divisible by 3. If yes find the quotient

(7 posts)

1. 

   mystry
   Member
   Posted 7 months ago #
   
   

   You are given with Binary Representation of a Number.
   Using only BitWise operation (No *, / , %) Find if the Number is divisible by 3.
   If yes, then return the quotient. else return -1.

2. 

   aks
   guest
   Posted 7 months ago #
   
   

   start from 0th bit and count the number of 1s alternatively i.e. 0th bit, 2ndbit, 4th bit....
   now start from 1st bit and count the number of 1s alternatively i.e. 1st bit, 3rdbit, 5th bit....
   if these two counts are equal,then num is div by 3

3. 

   RangaRao
   Member
   Posted 7 months ago #
   
   

   A good one..

4. 

   ashish
   guest
   Posted 7 months ago #
   
   

   @aks:
   whats logic behind this??

5. 

   ashish
   guest
   Posted 7 months ago #
   
   

   @aks:
   whats logic behind this??

6. 

   techcoder
   Member
   Posted 7 months ago #
   
   

   @ aks and all above
   wrong solution
   counter Ex 21
   binary reprsenetation 00010101
   number of set even bits =3
   number of set odd bits =0
   both the counts are not equal but 21 is divisible by 3

   correct solution
   if(number of set bits at even position - number of set bits at odd position) is divisible by 3
   then the number is divisible by 3.

7. 

   mystry
   Member
   Posted 7 months ago #
   
   

   @All:
   Guys thanks for the solution to find whether the number is divisible by 3 or not. (I knew this solution already :P )

   My question is: If the number is divisible by 3 then what is quotient.
   ex 21 / 3 =7.
   now as 21 is divisible by 3 then the output should be 7. otherwise the output should be Indivisible or -1.

8. 

   Guddu Sharma
   Member
   Posted 1 month ago #
   
   

   Use DFA concept.
   state=0;
   

   while(bits are remaining)//move from MSB to LSB
   {
   	if(bit==0)
   	{
   		if(state==0)
   			state=0;
   		else if(state==1)
   			state=2;
   		else if(state==2)
   			state=1;
   	}
   	else if(bit==1)
   	{
   		if(state==0)
   			state=1;
   		else if(state==1)
   			state=0;
   		else if(state==2)
   			state=2;
   	}
   } 
   
   if(state==0)
   	Number is divisible by 3;
   else
   	Not divisible by 3;

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