public void Should_count_inversions_even_when_large_input()
{
var arr = Enumerable.Range(1, 65911).ToArray();
var count = CountingInversions.CountInversions(arr);
Assert.Equal(0, count);
var arr2 = Enumerable.Range(1, 73099).ToArray();
var count2 = CountingInversions.CountInversions(arr2);
Assert.Equal(0, count2);
var arr3 = Enumerable.Range(1, 32688).ToArray();
var count3 = CountingInversions.CountInversions(arr3);
Assert.Equal(0, count3);
var arr4 = Enumerable.Range(1, 100000).Reverse().ToArray();
var count4 = CountingInversions.CountInversions(arr4);
Assert.Equal(4999950000, count4);
var arr5 = Enumerable.Range(1, 100000).Reverse().ToArray();
var count5 = CountingInversions.CountInversions(arr5);
Assert.Equal(4999950000, count5);
}
public void Should_count_inversions(int[] arr, long expected)
{
var count = CountingInversions.CountInversions(arr);
AssertHelpers.AssertIsSorted(arr);
Assert.Equal(expected, count);
}