Split list based on value without groups

Question

I want to split my list by value, but I don't need group the result, this is my list :

var source = new List<Car>() {
    new Car() { ID = 1, Model = "Model A" },
    new Car() { ID = 2, Model = "Model B" },
    new Car() { ID = 3, Model = "Model B" },
    new Car() { ID = 4, Model = "Model B" },
    new Car() { ID = 5, Model = "Model A" },
    new Car() { ID = 6, Model = "Model A" }
};
var result = GetListOfAdjacentCarsOfSameModel();

I want the resulting list to look like this:

- Model A
    - ID = 1, Model = "Model A"
- Model B
    - ID = 2, Model = "Model B"
    - ID = 3, Model = "Model B"
    - ID = 4, Model = "Model B" 
- Model A   
    - ID = 5, Model = "Model A"
    - ID = 6, Model = "Model A"

What do you mean you don't need to group the result? seems to me like the result you want is grouped by `Model` — vc 74, Feb 22 '18 at 10:23
You should at the very least provide code that compiles - what you show here does not. — DavidG, Feb 22 '18 at 10:23
Don't tell what you don't need but what you need. You want to group by adjacent duplicates? There are duplicate questions on stackoverflow — Tim Schmelter, Feb 22 '18 at 10:26
1. Do you want the output to be a `List>` or a list of strings as you show in your post? 2. Are you absolutely sure that your source data is `List>`? That makes no sense at all. — DavidG, Feb 22 '18 at 10:26
@vc74 i already try cars.GroupBy(m => m.Model); but the result it just return two datas, — onlyme, Feb 22 '18 at 10:27
@onlyme OK so as Tim pointed out you want to group the adjacent cars by `Model`, right? — vc 74, Feb 22 '18 at 10:29
@Weggo: The sample doesn't compile, because `result` is of type `List>` but you're adding `Car`s to it. — Tomas Aschan, Feb 22 '18 at 10:31
@vc74 not realy sure about _group_the_ adjacent _, but i need split the list to 3 based model — onlyme, Feb 22 '18 at 10:33
@onlyme, just to make it clear... why do the 2 cars in (3) not belong to (1)? — vc 74, Feb 22 '18 at 10:34
@MichaelRandall You can easily tell by the number of deleted answers ;) — vc 74, Feb 22 '18 at 10:36
@MichaelRandall Looking at your rep chart, you're doing pretty well, carry on like that and you'll pass me fairly soon! — DavidG, Feb 22 '18 at 10:38
Possible duplicate of https://stackoverflow.com/questions/14879197/linq-query-data-aggregation-group-adjacent — DavidG, Feb 22 '18 at 10:40
sorry all my question make confused hehe,, i just want to result like this from list above : - Model A - new Car() { ID = 1, Model = "Model A" } - Model B - new Car() { ID = 2, Model = "Model B" }, - new Car() { ID = 3, Model = "Model B" }, - new Car() { ID = 4, Model = "Model B" }, - Model B - new Car() { ID = 5, Model = "Model A" }, - new Car() { ID = 6, Model = "Model A" } — onlyme, Feb 22 '18 at 11:00
@onlyme I think you mean Model A in the last group. So you want to group adjacent cars with the same model together? — vc 74, Feb 22 '18 at 11:54

score 1 · Answer 1 · answered Feb 22 '18 at 10:34

I suggest a simple loop:

var result = new List<List<Car>>();

foreach (var item in source)
  if (result.Count <= 0 || result[result.Count - 1][0].Model != item.Model)
    result.Add(new List<Car>() {item}); // Create a new group, add item to it
  else
    result[result.Count - 1].Add(item); // Add item into the last group

score 0 · Answer 2 · answered Feb 22 '18 at 10:39

public class Car
{
    public int ID { get; set; }
    public string Model { get; set; }
}

public class Result
{
    public string Model { get; set; }
    public int Count { get; set; }
}

var source = new List<Car>();
source.Add(new Car { ID = 1, Model = "Model A" });
source.Add(new Car { ID = 1, Model = "Model B" });
source.Add(new Car { ID = 1, Model = "Model B" });
source.Add(new Car { ID = 1, Model = "Model B" });
source.Add(new Car { ID = 1, Model = "Model A" });
source.Add(new Car { ID = 1, Model = "Model A" });

var result = new List<Result>();
if (source.Any())
{
    string model = source[0].Model;
    int count = 0;
    foreach (var car in source)
    {
        if (car.Model == model)
        {
            count++;
        }
        else
        {
            result.Add(new Result { Model = model, Count = count });
            model = car.Model;
            count = 1;
        }
    }
    result.Add(new Result { Model = model, Count = count });
}

foreach (var r in result)
{
    Console.WriteLine(r.Model + " - " + r.Count);
}

Tomas Aschan · Answer 3 · 2018-02-22T11:43:45.557

I'm struggling with finding a simple way to do this, but you can always do it iteratively:

var source = new List<string>() {
    "Model A",
    "Model B",
    "Model B",
    "Model B",
    "Model A",
    "Model A"
};

string lastModel = null;
List<string> currentList = new List<string>();
var result = new List<List<string>>();

foreach (var model in source)
{
    if (lastModel != null && model != lastModel)
    {
        result.Add(currentList);
        currentList = new List<string>();
    }
    currentList.Add(model);
    lastModel = model;
}

if (currentList.Any()) {
    result.Add(currentList);
}

Now, it's easy to wrap that code in an extension method you can use on your car class:

var source = new List<Car>() {
    new Car { Model = "Model A" },
    new Car { Model = "Model B" },
    new Car { Model = "Model B" },
    new Car { Model = "Model B" },
    new Car { Model = "Model A" },
    new Car { Model = "Model A" }
};

var result = source.CollectAdjacentWithSameModel();

// elsewhere    
public static class EnumerableExtensions
{
    public static IEnumerable<IEnumerable<Car>> CollectAdjacentWithSameModel(this IEnumerable<Car> source)
    {
        var lastModel = default(Car);
        List<Car> currentList = new List<Car>();
        var result = new List<List<Car>>();

        foreach (var model in source)
        {
            if (lastModel != null && model.Model != lastModel.Model)
            {
                result.Add(currentList);
                currentList = new List<Car>();
            }
            currentList.Add(model);
            lastModel = model;
        }

        if (currentList.Any())
        {
            result.Add(currentList);
        }

        return result;
    }
}

public class Car {
    public string Model { get; set; }
}

Not in a way I can think of using built-in LINQ functions, but it's trivial to wrap that in an extension method that you can use as part of a method chain. — Tomas Aschan, Feb 22 '18 at 11:40
@onlyme: I added an update that shows how to wrap this in a LINQ-compatible extension method. — Tomas Aschan, Feb 22 '18 at 11:44

Split list based on value without groups

3 Answers3