HorseBarn free response answer 2

The HorseBarn problem from the 2012 AP Computer Science Exam is typical of free response problems that test arrays.

Review the HorseBarn free response solution with AP CS Tutor Brandon Horn.

HorseBarn Part (a): findHorseSpace

  public int findHorseSpace(String name)
  {
    for(int i = 0; i < spaces.length; i++)
    {
      Horse h = spaces[i];
      if(h != null && name.equals(h.getName()))
          return i;
    }
    
    return -1;
  }

HorseBarn Part (b): consolidate

  public void consolidate()
  {
    int nextSpace = 0;

    for(int i = 0; i < spaces.length; i++)
    {
      if(spaces[i] != null)
      {
        spaces[nextSpace] = spaces[i];
        nextSpace++;
      }
    }

    for(int i = nextSpace; i < spaces.length; i++)
      spaces[i] = null;
  }

HorseBarn Part (b): consolidate – alternate solution 1

  public void consolidate()
  {
    Horse[] newSpaces = new Horse[spaces.length];
    int newIndex = 0;
    
    for(int oldIndex = 0; oldIndex < spaces.length; oldIndex++)
    {
      if(spaces[oldIndex] != null)
      {
        newSpaces[newIndex] = spaces[oldIndex];
        newIndex++;
      }
    }
    
    spaces = newSpaces;
  }

HorseBarn Part (b): consolidate – alternate solution 2

public void consolidate()
{
  for(int i = 0; i < spaces.length; i++)
  {
    if(spaces[i] == null)
    {
      int nextHorse = i + 1;
      while(nextHorse < spaces.length && spaces[nextHorse] == null)
        nextHorse++;

      if(nextHorse < spaces.length)
      {
        spaces[i] = spaces[nextHorse];
        spaces[nextHorse] = null;
      }
    }
  }
}