Question

I have this pattern where I need to select any random element from a list, other than the current one (passed as argument). I came up with this method:

public Element GetAnyoneElseFromTheList(Element el)
{
  Element returnElement = el;
  Random rndElement = new Random();
  if (this.ElementList.Count>2) 
  {
  while (returnElement == el) 
  {
    returnElement = this.ElementList[rndElement.Next(0,this.ElementList.Count)];  
  }

  return returnElement;
  }
 else return null;
}

But that while loop has been bothering me for days and nights and I need to get some sleep. Any other good approaches to this? ie. something that returns in a fixed-number-of-steps ?

Edit : In my case, the list is guaranteed to contain the “el” Element to avoid, and the list contains no duplicates, but it would be interesting to see some more general cases aswell.

Answer 1

public Element GetAnyoneElseFromTheList(Element el)
{
  Random rndElement = new Random();
  int index;
  if (this.ElementList.Count>1) 
  {
     index = rndElement.Next(0,this.ElementList.Count-1);
     if (this.ElementList[index] == el)
        return this.ElementList[this.ElementList.Count-1];
     else
        return this.ElementList[index];
  }
 else return null;
}