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linqienumerableyield-returngeneric-function
delphie
delphie

Reputation: 1

How to make a version of LINQ OrderBy, which uses a Radix Sort for Dates

This specification requires the algorithm to have the lowest possible order of complexity. I am trying to create my own version of LINQ .OrderBy() to achieve this, using a Radix Sort.

IE I am trying to create

var sortedListOfAppointments = listOfAppointments.OrderByDateUsingRadixSort(a => a.AppointmentDateTime);

I currently have a method which accepts any IEnumerable list, and sorts by the stated date field, but at the moment, it only returns the sorted Dates, not the sorted list.

To start with, I have a method which Sorts dates as follows:-

public static IEnumerable<DateTime> SortDatesUsingRadixSort(this IEnumerable<DateTime> dates)

Then I have a method to accept any class, and use the stated field as the field to sort by

public static IEnumerable<DateTime> OrderByDateUsingRadixSort<TSource>(this IEnumerable<TSource> dates, Func<TSource, DateTime> selector) =>
    (from date in dates select selector(date)).SortDatesUsingRadixSort();

This works, returns a list of sorted dates, and can be used as follows:-

var sortedDates = listOfAppointments.OrderByDateUsingRadixSort(a => a.AppointmentDateTime);

But I am wanting

var sortedListOfAppointments = listOfAppointments.OrderByDateUsingRadixSort(a => a.AppointmentDateTime);

IE, I am wanting OrderByDateUsingRadixSort to return IEnumerable, but what needs to change in this method to achieve it?

public static IEnumerable<TSource> OrderByDateUsingRadixSort<TSource>(this IEnumerable<TSource> dates, Func<TSource, DateTime> selector) =>
    // what needs to change to return the whole list sorted?       (from date in dates select selector(date)).SortDatesUsingRadixSort();

I feel like I am missing something small but fundamental in my understanding here.

Sources used to get this far:- https://www.geeksforgeeks.org/how-to-efficiently-sort-a-big-list-dates-in-20s/ https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/how-to-add-custom-methods-for-linq-queries

Upvotes: 0

Views: 49

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