Divide even number until the result is an odd number

Question

I'm trying to divide a number by 2 if it's even, until each operation returns an odd number, so for example, dividing 16 by 2 returns 8 which dividing by 2 returns 4 until it gets to 2.

I've tried using recursion but it's performing really badly so I wrote the code below instead...the problem is that it's only dividing one time:

public int InchFraction(int value)
{
    for (int i = 0; i < value; i++)
    {
        if (value % 2 == 0)
        {
            value = value / 2;
            return value;
        }
    }
    return value;
}

InchFraction(16) //it's returning 8

Answer 1

public int InchFraction(int value)
{
    while (value % 2 == 0) 
        value /= 2;
    return value;
}

or since you are trying to optimise, try this

private static int countDivOps = 0;
private static int countCalls = 0;
static ulong M2(ulong v, int p = 32)
{
  var d = 1UL << p;
  countCalls++;
  while (v % d == 0) 
  {
    v /= d;
    countDivOps++;
  }
  return d == 2 ? v : M2(v, p / 2);
}
static void Main(string[] args)
{
  var v = 0x1204000000000000ul;
  var rv = M2(v);
  Console.WriteLine($"{v} reduces to {rv}(0x{rv:X}) in {countCalls} calls after (2x) {countDivOps} division operations");

It's not pretty and I leave you to play with your debugger and see what it's doing but FWIW the output is...

1298162592589545472 (0x1204000000000000) reduces to 1153(0x481) in 6 calls after (2x) 3 division operations

Note that the cost of the code is not all about division operations and calls, this was just to illustrate how you might approach this sort of problem.