/*!
* Shuffle an array. Found on https://dotnetperls.com/fisher-yates-shuffle
*/
public static void Shuffle <T>(T[] state)
{
int l = state.Length;
for (int i = 0; i < l; i++)
{
//! NextDouble returns a double from
//! 0 to 1
int r = i + (int)(_random.NextDouble() * (l - i));
NPuzzleUtils.Swap(state, i, r);
}
}
/*!
* Don't test for inversions with the largest
* element in the array
*/
public void TestCountInversions()
{
int[] s1 = { 9, 8, 7, 6, 5, 4, 3, 2, 1 };
Assert.AreEqual(NPuzzleUtils.CountInversions(s1), 28);
NPuzzleUtils.Swap(s1, 1, 2);
Assert.AreEqual(NPuzzleUtils.CountInversions(s1), 27);
int[] s2 = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
Assert.AreEqual(NPuzzleUtils.CountInversions(s2), 0);
NPuzzleUtils.Swap(s2, 7, 8);
Assert.AreEqual(NPuzzleUtils.CountInversions(s2), 0);
NPuzzleUtils.Swap(s2, 6, 7);
Assert.AreEqual(NPuzzleUtils.CountInversions(s2), 0);
}
// TODO: again, NPuzzleState return type instead of int[]
public override NPuzzleState <int[]> Result(NPuzzleState <int[]> s, int action)
{
int[] state = s.State;
int[] newState = new int[state.Length];
int emptyIndex;
state.CopyTo(newState, 0);
emptyIndex = GetEmptyIndex(state);
if (emptyIndex == -1)
{
NPuzzleUtils.MissingEmptyElementException ex = new NPuzzleUtils.MissingEmptyElementException(state.Length.ToString());
throw ex;
}
if (AcceptableAction(state, emptyIndex, action))
{
if (action == 1)
{
NPuzzleUtils.Swap(newState, emptyIndex, emptyIndex + 1);
}
else if (action == -1)
{
NPuzzleUtils.Swap(newState, emptyIndex, emptyIndex - 1);
}
else if (action == -2)
{
NPuzzleUtils.Swap(newState, emptyIndex, emptyIndex + dimension);
}
else
{
NPuzzleUtils.Swap(newState, emptyIndex, emptyIndex - dimension);
}
}
else
{
String msg = String.Format("You entered an invalid action: {0} for the state {1}", action, state.ToString());
NPuzzleUtils.ResultAcceptableActionException ex = new NPuzzleUtils.ResultAcceptableActionException(msg);
throw ex;
}
return(new NPuzzleState <int[]>(newState));
}