C# Sort a list based on values in another list efficiently

Question

Say I have a list of cars:

List<string> carList = new List<string>(){"Car1", "Car2", "Car3"};

I then have prices assigned to each car in another list where the first item corresponds to Car1 etc:

List<int> priceList = new List<int>(){50, 200, 10};

Now I want to sort my carList based on the highest price in priceList, with the expected outcome of my carList now having the order like this:

"Car2", "Car1", "Car3"

This needs to be done as fast as possible, it is the only thing that matters. It doesn't matter if carList is sorted itself or if I need to create a new list to store the sorted values in. I don't have any use of priceList after this sorting is completed and don't need its values.

so what did you try yourself already? SO isn't a code-writing-service whom you can give a task "give me the code". You have to provide some own affords. — MakePeaceGreatAgain
– MakePeaceGreatAgain, Commented Feb 18, 2022 at 10:18
anyway, why don't you just create a Car-class with properties like "Name" and "Price"? Then it's pretty easy to have a list of those instances and sort that. — MakePeaceGreatAgain
– MakePeaceGreatAgain, Commented Feb 18, 2022 at 10:20
I could probably provide some loop which checks each value and sort them very inefficiently but that wouldn't really help you? I am trying to find what the most efficient way of doing it is. — eligolf
– eligolf, Commented Feb 18, 2022 at 10:21
In this case I can't have a class of items, the preconditions are given in the question. Is it possible to do what I ask about? — eligolf
– eligolf, Commented Feb 18, 2022 at 10:21
"sort them very inefficiently" Well, we cannot help you much, as we simply have no clue if "our" solution is in any way better than "your" one. Furthermore "Fastest" highly depends on your data: how much data is it and how often do you change that data, e.g. add items to both lists or remove them? — MakePeaceGreatAgain
– MakePeaceGreatAgain, Commented Feb 18, 2022 at 10:25

Astrid E. · Accepted Answer · 2022-02-18 10:28:17Z

1

You can benefit from Linq's .Zip() to associate price with car name, then order by price, then select the car names.

List<string> sortedCars = carList
    .Zip(priceList,
        ( car, price ) => ( Name: car, Price: price))
    .OrderByDescending(car => car.Price)
    .Select(car => car.Name)
    .ToList();

Example fiddle here;

answered Feb 18, 2022 at 10:28

Astrid E.

2,9222 gold badges13 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

eligolf Over a year ago

This works great thank you! Is it fast though?

Astrid E. Over a year ago

You're welcome! I don't know whether it's faster than the other suggested approaches, unfortunately.

J.Salas · Accepted Answer · 2022-02-18 10:27:33Z

0

Having the price on other List only related by the 'id' of both of them is a handicap, so I go for a intermediate List with both values, then sort it and cast it again to the original class list, a little unefficient, but you have little options to start with

List<string> cartests = carList.Select(
        (item, index) => new cartest() 
           { carName= item, carPrice = priceList[index] })
    .OrderByDescending(o=> o.carPrice )
    .Select(itemo=> itemo.carName).ToList();

Intermediate class

    private class cartest 
    { 
        public string carName{ get; set; }
        public int carPrice { get; set; }
    }

answered Feb 18, 2022 at 10:27

J.Salas

1,3711 gold badge10 silver badges19 bronze badges

Comments

Matthew Watson · Accepted Answer · 2022-02-18 10:51:35Z

0

If you can use arrays instead of lists, you can use Array.Sort(Array, Array) to sort two arrays at the same time.

Otherwise you will have to convert your lists to an array, sort the arrays, and then convert back:

List<string> carList = new List<string> { "Car1", "Car2", "Car3" };
List<int> priceList = new List<int> { 50, 200, 10 };

var carArray = carList.ToArray();

Array.Sort(priceList.ToArray(), carArray, Comparer<int>.Create((a, b) => b.CompareTo(a)));

carList = carArray.ToList();

The Comparer<int>.Create() is to reverse the sort order.

answered Feb 18, 2022 at 10:51

Matthew Watson

111k12 gold badges179 silver badges301 bronze badges

Collectives™ on Stack Overflow

C# Sort a list based on values in another list efficiently

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related