How to write....**

[krichait]

write a program of any adding or subtracting or multiplication "WITHOUT"
using Arithmetic Operators, Union operators.. Asked in .....CTS....

hint: can use Bitwise operators

[Norm]

Is this an assignment? Have you written some code you need help with?

[krichait]

Is this an assignment? Have you written some code you need help with?

Thanks for response... this is not an assignment .. but asked in an interview... . I tried .. using bitwise operators...


int add(int a, int b)
{
return add((a & b) << 1, a ^ b));
}

but actually it is not working...

[mtv134]

I can see ur using recursing
where is the break condition?

[Norm]

Here's cod to do it bit by bit.

// Add two ints using bitwise operators

public class ArithWithBitOps {
   //------------------------------------------------------------------------------
   // Second attempt  -  Go bit by bit right to left doing binary arith
   static int carry = 0;  // c=1 for 1+1

   static int add2(int a, int b) {
      int sum = 0;                     // get sum here
      int mask = 1;                    // shifting mask used to test each bit

      while(mask != 0) { 
         int ta = a & mask;                  // get next bit to add
         int tb = b & mask;                  // get next bit to add
         int bsum = bitAdd2(ta, tb, mask);   // add the bits & set carry
         if(Testing) System.out.print("ta=" + ta + ", tb=" + tb + ", bsum=" + bsum 
                           + ", carry=" + carry + ", b4sum=" + sum);
         sum = (sum | bsum);                 // OR in the results
         if(Testing) System.out.println(", aft sum=" + sum);
         mask = mask << 1;                   // move to next bit
      } // end while() thru bits

      if(carry > 0) System.err.println(">>>>>>>>>>>>losing carry");
      return sum;
   } // end add2()

   //----------------------------------------------------------
   // Add two selected  bits in x and y & set carry if carry
   static int bitAdd2(int x, int y, int bsel) {
//      System.out.println("bitAdd2 of " + x + " " + y);
      int tx = x & bsel;
      int ty = y & bsel;
      if(carry == 1) {  // Have carry ?
         if((tx & ty) != 0) {
            carry = 1;
            return bsel;    // 1 + 1 + c=1 -> 1 + c=1
         }else if((tx ^ ty) != 0) {
            carry = 1;
            return 0;      // 1 + 0 + c=1 -> 0 + c=1
         }else {
            carry = 0;
            return bsel;   // 0 + 0 + c=1 -> 1 + c=0
         }
      }else if (carry == 0) { // no carry
         if((tx & ty) > 0) {
            carry = 1;
            return 0;      // 1 + 1 + c=0 -> 0 + c=1
         }else if((tx ^ ty) != 0) {
            carry = 0;
            return bsel;   // 1 + 0 + c=0 -> 1 + c=0
         }else {
            System.out.println("(tx ^ ty)=" + (tx ^ ty));
            carry = 0;
            return 0;      // 0 + 0 + c=0 -> 0 + c=0
         }
      }else {
         System.err.println("Invalid carry= " + carry);
         return 0;
      }
   } // end bitAdd2()

   //------------------------------------------------
   // Test the above
   public static void main(String[] args) {
      // The numbers to add
      int x = -24;
      int y = 15;

      if(Testing) System.out.println("Max int=" + Integer.MAX_VALUE   //Max int=2147483647
           + " " + Integer.toHexString(-2)  //-2=fffffffe
           + " " + 0x80000000);    //-2147483648
      int sum = add2(x, y);
      System.out.println("Final sum= " + sum + " vs " + (x + y) + "    " + Integer.toHexString(sum));
                        //Final sum= -9 vs -9    fffffff7  
   } // end main()

   static final boolean Testing = false;  // global flag for debug output
}

[Niveditha]

Wow norm...
Good job...

[krichait]

Wonderful.... NORM....

Thanks vey much.............

[Norm]

I don't see how you could answer this question in a interview. My version took a couple of hours.

[mtv134]

Nice work Norm

[krichait]

I don't see how you could answer this question in a interview. My version took a couple of hours.

It was asked to my friend.. in Cognizant Technology ...Company... they just give him to slove this problem in 45 minutes... but he couldn't... if he does the problem he got he job....

Any Way.......... I got the code... but it is really unusefull to write such a code for simple addition....

Thanks a lot..........