/// <summary>
/// This method finds the smallest value in the given distance array. If the smallest value appears more than once,
/// then the lower index is returned.
/// </summary>
/// <param name="distances">The pre-calculated distance matrix.</param>
/// <returns>The first smallest distance index.</returns>
public static int[] FirstSmallestDistanceIndex(decimal[,] distances)
{
if (ParameterValidation.IsDecimalArrayNullOrEmpty(distances))
{
return(null);
}
var indexSmallest = new[] { 0, 0 };
//var indexSmallestA = 0;
//var indexSmallestB = 0;
for (int indexA = distances.GetLowerBound(0); indexA <= distances.GetUpperBound(0); indexA++)
{
for (int indexB = distances.GetLowerBound(1); indexB <= distances.GetUpperBound(1); indexB++)
{
if ((indexA != indexB) && ((indexSmallest[0] == indexSmallest[1]) || (Math.Abs(distances[indexA, indexB]) < Math.Abs(distances[indexSmallest[0], indexSmallest[1]]))))
{
indexSmallest[0] = indexA;
indexSmallest[1] = indexB;
}
}
}
return(indexSmallest); // new int[] { indexSmallestA, indexSmallestB };
}
/// <summary>
/// This method finds the next smallest value in the array, after the value found in the index specified. If the same
/// value exists multiple times, the lower index is returned.
/// </summary>
/// <param name="distances">The pre-calculated distance matrix.</param>
/// <param name="indexLast"></param>
/// <returns>The next smallest distance index from the last indexes.</returns>
public static int[] NextSmallestDistanceIndex(decimal[,] distances, int[] indexLast)
{
if (ParameterValidation.IsDecimalArrayNullOrEmpty(distances))
{
throw new ArgumentOutOfRangeException(nameof(distances));
}
if (ParameterValidation.IsIntArrayNullOrEmpty(indexLast))
{
throw new ArgumentOutOfRangeException(nameof(indexLast));
}
var indexBest = new[] { -1, -1 };
//var indexBestA = -1;
//var indexBestB = -1;
if ((indexLast[0] == -1) || (indexLast[1] == -1))
{
return(FirstSmallestDistanceIndex(distances));
}
for (int indexA = distances.GetLowerBound(0); indexA <= distances.GetUpperBound(0); indexA++)
{
for (int indexB = distances.GetLowerBound(1); indexB <= distances.GetUpperBound(1); indexB++)
{
if
//// Not the same object twice / no distance measurement ... zero.
((indexA != indexB)
&&
//// Not the same indexes the other way around as last time (at least one value changed).
(indexLast[0] != indexB || indexLast[1] != indexA)
&&
//// Not the same indexes the same way around as last time (at least one value changed).
(indexLast[0] != indexA || indexLast[1] != indexB)
&&
//// Distance can be the same as the last one - if the index is higher.
((Math.Abs(distances[indexA, indexB]) == Math.Abs(distances[indexLast[0], indexLast[1]]) && (indexA > indexLast[0] || (indexA >= indexLast[0] && indexB > indexLast[1])))
||
//// Distance can be more, but only if it is less than the best found so far.
(Math.Abs(distances[indexA, indexB]) > Math.Abs(distances[indexLast[0], indexLast[1]]) && (indexBest[0] == -1 || indexBest[1] == -1 || Math.Abs(distances[indexA, indexB]) < Math.Abs(distances[indexBest[0], indexBest[1]])))))
{
indexBest[0] = indexA;
indexBest[1] = indexB;
if (distances[indexA, indexB] == distances[indexLast[0], indexLast[1]])
{
// If the distance is the same, then it is impossible to find a lower one, so break out, also, if no break, indexes may be skipped.
break;
}
}
}
}
return(indexBest); //new int[] { indexBestA, indexBestB };
}
