public void QuickSelectFindsGreatestElement()
{
var list = _list;
var qs = new Quickselect<double>();
var smallestIndex = qs.Select(list, Length - 1);
smallestIndex.Should().Be(Length - 1, "because quickselect returns a partially ordered list right of the returned index which is greater or equal - and that list must be empty for the greatest element");
var smallestElement = list[smallestIndex];
smallestElement.Should().Be(list.Max(), "because that is the greatest element");
}
public void QuickSelectFindsSecondSmallestElement()
{
var list = _list;
var qs = new Quickselect<double>();
var secondSmallestIndex = qs.Select(list, 1);
secondSmallestIndex.Should().Be(1, "because quickselect returns a partially ordered list left of the returned index which is smaller - and there must only be one element to the left");
var secondSmallestElement = list[secondSmallestIndex];
secondSmallestElement.Should().BeGreaterThan(list[0], "because the element left of the returned index should be smaller");
secondSmallestElement.Should().BeLessOrEqualTo(list[2], "because the elements right of the returned index should be greater or equal");
list.Skip(2).Should().OnlyContain(value => value >= secondSmallestElement, "because all elements right of the returned index should be greater or equal");
}
public void QuickSelectFindsNthSmallestElement()
{
var list = _list;
var qs = new Quickselect<double>();
var n = Length / 2;
var index = qs.Select(list, n);
index.Should().BeInRange(0, Length - 1, "because we expect the result to be a list index");
var element = list[index];
list.Take(n).Should().OnlyContain(value => value < element, "because all elements left of the returned index should be smaller");
list.Skip(n).Should().OnlyContain(value => value >= element, "because all elements right of the returned index should be greater or equal");
}
public void RecursiveQuickSelectFindsSmallestElement()
{
var list = _list;
var qs = new Quickselect <double>();
var smallestIndex = qs.SelectRecursive(list, 0);
smallestIndex.Should().Be(0, "because quickselect returns a partially ordered list left of the returned index which is smaller - and that list must be empty for the smallest element");
var smallestElement = list[smallestIndex];
smallestElement.Should().Be(list.Min(), "because that is the smallest element");
}
public void QuickSelectFindsGreatestElement()
{
var list = _list;
var qs = new Quickselect <double>();
var smallestIndex = qs.Select(list, Length - 1);
smallestIndex.Should().Be(Length - 1, "because quickselect returns a partially ordered list right of the returned index which is greater or equal - and that list must be empty for the greatest element");
var smallestElement = list[smallestIndex];
smallestElement.Should().Be(list.Max(), "because that is the greatest element");
}
public void RecursiveQuickSelectFindsNthSmallestElement()
{
var list = _list;
var qs = new Quickselect <double>();
var n = Length / 2;
var index = qs.SelectRecursive(list, n);
index.Should().BeInRange(0, Length - 1, "because we expect the result to be a list index");
var element = list[index];
list.Take(n).Should().OnlyContain(value => value < element, "because all elements left of the returned index should be smaller");
list.Skip(n).Should().OnlyContain(value => value >= element, "because all elements right of the returned index should be greater or equal");
}
public void RecursiveQuickSelectFindsSecondSmallestElement()
{
var list = _list;
var qs = new Quickselect <double>();
var secondSmallestIndex = qs.SelectRecursive(list, 1);
secondSmallestIndex.Should().Be(1, "because quickselect returns a partially ordered list left of the returned index which is smaller - and there must only be one element to the left");
var secondSmallestElement = list[secondSmallestIndex];
secondSmallestElement.Should().BeGreaterThan(list[0], "because the element left of the returned index should be smaller");
secondSmallestElement.Should().BeLessOrEqualTo(list[2], "because the elements right of the returned index should be greater or equal");
list.Skip(2).Should().OnlyContain(value => value >= secondSmallestElement, "because all elements right of the returned index should be greater or equal");
}
public void QuickSelectFindsSmallestElement()
{
var list = _list;
var qs = new Quickselect<double>();
var smallestIndex = qs.Select(list, 0);
smallestIndex.Should().Be(0, "because quickselect returns a partially ordered list left of the returned index which is smaller - and that list must be empty for the smallest element");
var smallestElement = list[smallestIndex];
smallestElement.Should().Be(list.Min(), "because that is the smallest element");
}
