Sort a list in C# by range and sameness

Question

I have a large list of hardware parts, where each part has a name and sales count.

Sample collection below:

var parts = new List<(string name, int sales)>{
    ("Part A", 400),
    ("Part B", 600),
    ("Part A", 600),
    ("Part C", 400),
    ("Part D", 1500),
    ("Part B", 500),
    ("Part A", 475),
    ("Part B", 400),
    ("Part E", 700),
    ("Part A", 700),
};

This list of parts is sorted, first by the sales count:

var results = parts.OrderByDescending(p => p.sales).ToList();

/*
Results:

Part D - 1500 
Part E - 700 
Part A - 700 
Part B - 600 
Part A - 600 
Part B - 500 
Part A - 475 
Part A - 400 
Part C - 400 
Part B - 400 
*/

Now, the second ordering I need is for same part names to be together as long as their sales are within a range of 100 of each other, but keeping the first ordering intact.

/*
Final results:

Part D - 1500 
Part E - 700 
Part A - 700 
Part A - 600 
Part B - 600 
Part B - 500 
Part B - 400 
Part A - 475 
Part A - 400 
Part C - 400
*/

How can this be achieved in an efficient way, so that it also performs well on large datasets?

Please check https://stackoverflow.com/questions/2779375/order-a-list-c-by-many-fields for an answer. — Rajan Patekar, Jun 08 '21 at 07:59
Didn't you ask almost the same question a few days ago? https://stackoverflow.com/questions/67869527/sort-a-list-in-c-sharp-by-custom-index-and-sameness/67869940 — Klamsi, Jun 08 '21 at 08:25
@Klamsi That other question is similar, but not the same or close to what this question is about. Thanks. — Nick, Jun 08 '21 at 08:27

score 1 · Answer 1 · answered Jun 08 '21 at 08:05

1

does this solve it?

var results = parts
   .OrderByDescending(p => Math.Floor(p.sales/100))
   .ThenBy(p => p.name)
   .ToList();

answered Jun 08 '21 at 08:05

Matthias L

101
4

1

Thanks Matthias. Unfortunately, it doesn't group same part names within range, together. – Nick Jun 08 '21 at 08:13

score 1 · Accepted Answer · answered Jun 08 '21 at 09:04

It depends on what "large datasets" means.

var parts = new List<(string Name, int Sales)?>{
    ("Part A", 400),
    ("Part B", 600),
    ("Part A", 600),
    ("Part C", 400),
    ("Part D", 1500),
    ("Part B", 500),
    ("Part A", 475),
    ("Part B", 400),
    ("Part E", 700),
    ("Part A", 700),
};

parts = parts.OrderByDescending(p => p.Value.Sales).ToList();

List<(string Name, int Sales)> sortedParts = new();

for (int i = 0; i < parts.Count; i++)
{
    if (parts[i] is not null)
    {
        sortedParts.Add(parts[i].Value);

        for (int j = i+1; j < parts.Count; j++)
        {
            if (parts[j] is not null && parts[i].Value.Name == parts[j].Value.Name 
                && parts[j].Value.Sales >= sortedParts.Last().Sales - 100
                && parts[j].Value.Sales <= sortedParts.Last().Sales + 100)
            {
                sortedParts.Add(parts[j].Value);
                parts[j] = null;
            }
        }
    }
}

Thanks Klamsi. Clever use of nullable value type tuples. Works well for most scenarios. I'll test it a bit more. — Nick, Jun 08 '21 at 10:57

Sort a list in C# by range and sameness

2 Answers2