/// <summary>
/// Uses binary search algorithm to find a distinct group of specific items in a nested collection that contains
/// sorted sub collections
/// </summary>
/// <typeparam name="T"> Type of base element </typeparam>
/// <param name="nestedCollection"> Collection of collections to iterate through to find distinct group frequency </param>
/// <param name="group"> group of elements to find the frequency of </param>
/// <returns> New group object of the group to find and their frequency </returns>
internal static int CalculateFrequencyOfGroup <T>(IEnumerable <IList <T> > nestedCollection,
IList <T> group) where T : IComparable <T>, IEquatable <T>
{
int count = 0;
foreach (var collection in nestedCollection)
{
var length = collection.Count;
var groupCounter = 0;
for (var i = 0; i < group.Count; i++)
{
bool found = false;
int index = BinarySearchHelper.BinarySearch(collection, 0, length - 1, group[i]);
if (index >= 0)
{
found = true;
}
// If the value is not found in the collection
if (!found)
{
continue;
}
else
{
groupCounter++;
}
}
if (groupCounter == group.Count)
{
count++;
}
}
return(count);
}
/// <summary>
/// Uses binary search algorithm to find the frequency of a single value when passed a flat sorted collection.
/// </summary>
/// <typeparam name="T"> Primitive type of the elements in collection </typeparam>
/// <param name="collection"> Flat sorted collection passed </param>
/// <param name="value"> Value to find the frequency of </param>
/// <returns>
/// New Singles object with the value and number of occurrences. Will return Item as null if passed null
/// </returns>
internal static Singles <T> CalculateSinglesSorted <T>(IList <T> collection, T value) where T : IComparable <T>, IEquatable <T>
{
var length = collection.Count;
int index = BinarySearchHelper.BinarySearch(collection, 0, length - 1, value);
// If the value is not found in the collection
if (index == -1)
{
return(new Singles <T> {
Item = value, Frequency = 0
});
}
// When an element is found count all occurrences to the left
var count = 1;
var left = index - 1;
while (left >= 0 && collection[left].Equals(value))
{
count++;
left--;
}
// Then count all occurrences to the right
var right = index + 1;
while (right < length && collection[right].Equals(value))
{
count++;
right++;
}
return(new Singles <T> {
Item = value, Frequency = count
});
}
