How to multiple two positive integers without multiplication or division operators or loops

Question

I need to multiply two integers without using multiplication or division operators, any built in Multiply functions, or loops.

I have managed to do multiplication with with a loop, but I don't get how to do so without loops.

Here is my solution with a loop:

Public Double(Double x, Double y)
{
 Double Result;
 Result =0;
 If(x==0 || y==0)
 {
   Result = 0;
  }
 else
 {
  for(int i=0; i<=y; i++)
   {
     Result = Result + x;   
   }
 }
        return Result;
}

You accept doubles, and yet your method only works if `y` is an integer. Do you *actually* need to support floating point numbers? You also don't support negative numbers properly. — Servy, Apr 25 '16 at 15:43
Then make your method accept an integer type, not a floating point type. — Servy, Apr 25 '16 at 15:45
Oh, and you also have a bunch of compiler errors in your code, if you're going to proport that the code is working code, you should be posting working code. — Servy, Apr 25 '16 at 15:46
I have tested code and it does work,... just for simplicity I am consider interger — K.Z, Apr 25 '16 at 15:47
The code that you posted doesn't work. The code that you posted doesn't even compile, for a multitude of reasons. If you have actual working code, then post that working code, because this isn't it. — Servy, Apr 25 '16 at 15:49

score 0 · Answer 1 · answered Apr 25 '16 at 15:58

You can do something like below in your function

        List<int> temp = new List<int>();
        temp.AddRange(Enumerable.Repeat(x,y));

        var result = test.Sum();

where your 'y' variable would be an integer count. However I'm not sure what exactly you are looking for

score 0 · Answer 2 · edited May 23 '17 at 11:52

I need to multiply two integers without using multiplication or division operators, any built in Multiply functions, or loops.

Reading the condition of your question, I think that the idea here is to use a smarter way for calculation, for example bitwise operations.

Based on the answers in How to perform multiplication, using bitwise operators? I suggest the following solution for your problem:

    public int MultiplyBitwise(int a, int b)
    {
        int product = 0;
        while (b > 0)
        {
            product += ((b & 1) > 0) ? a : 0;
            a <<= 1;
            b >>= 1;
        }

        return product;
    }

How to multiple two positive integers without multiplication or division operators or loops

2 Answers2