/// <summary>
/// Creates an unordered array of subsetCount int indices that
/// constitute a subset of all ints in the range [0, count-1].
/// O(subsetCount) for subsetCount << count.
/// NOTE: It is assumed that subsetCount is significantly smaller
/// than count. If this is not the case, use
/// CreateRandomSubsetOfSize instead.
/// WARNING: As subsetCount approaches count execution time
/// increases significantly.
/// </summary>
public static int[] CreateSmallRandomSubsetIndexArray(
this IRandomUniform rnd, int subsetCount, int count)
{
Requires.That(subsetCount >= 0 && subsetCount <= count);
var subsetIndices = new IntSet(subsetCount);
for (int i = 0; i < subsetCount; i++)
{
int index;
do
{
index = rnd.UniformInt(count);
}while (!subsetIndices.TryAdd(index));
}
return(subsetIndices.ToArray());
}
/// <summary>
/// Creates an unordered array of subsetCount int indices that
/// constitute a subset of all ints in the range [0, count-1].
/// O(subsetCount) for subsetCount << count.
/// NOTE: It is assumed that subsetCount is significantly smaller
/// than count. If this is not the case, use
/// CreateRandomSubsetOfSize instead.
/// WARNING: As subsetCount approaches count execution time
/// increases significantly.
/// </summary>
public static int[] CreateSmallRandomSubsetIndexArray(
this IRandomUniform rnd, int subsetCount, int count)
{
if (!(subsetCount >= 0 && subsetCount <= count))
{
throw new ArgumentOutOfRangeException(nameof(subsetCount));
}
var subsetIndices = new IntSet(subsetCount);
for (int i = 0; i < subsetCount; i++)
{
int index;
do
{
index = rnd.UniformInt(count);
}while (!subsetIndices.TryAdd(index));
}
return(subsetIndices.ToArray());
}