How to remove sublists with lowest counts and keep the one with the highest count from the main list?

Question

I have a list of sublists which is as List<List<nodes>>. I have stored some lists in the List of lists that now i refer to as the main list. Now i have to compare the counts of the elements in the sublists, that is lists that are stored in main list. I need to keep only that sublist which has the highest count amongst all the sublists and remove the remaining sublists. How to do that?

Answer 1

List<List<Foo>> mainList = ...

// Find count of biggest sub-list.
int maxCount = mainList.Max(list => list.Count);

// Remove all other sub-lists.
mainlist.RemoveAll(list => list.Count != maxCount);

Do note that if more there are multiple sub-lists with maximum-count, all of them will be retained.

If you don't want this, you could arbitrarily choose one of them to retain:

if(mainlist.Count != 1)
   mainList.RemoveRange(1, mainList.Count - 1);

If you don't care about performance, and you don't mind reassigning the variable, you could do:

mainList = mainList.OrderByDescending(list => list.Count)
                   .Take(1)
                   .ToList();

EDIT:

In .NET 2.0, you could do something like:

public static void KeepBiggestSubList<T>(List<List<T>> mainList)
{
    if (mainList == null)
        throw new ArgumentNullException("mainList");

    if (mainList.Count == 0)
        return;

    List<T> maxList = mainList[0];

    foreach (List<T> list in mainList)
    {
        if (list.Count > maxList.Count)
            maxList = list;
    }

    mainList.Clear();
    mainList.Add(maxList);
}