Question

I have a class that has a dictionary that stores string values and a list that stores unsigned 64-bit integers. This class is considered equal to another class of the same type if their dictionaries contain the same keys and values.

I also have a static list containing several instances of this class. I want to check if there are duplicate items in this list. If there are duplicates, I want to merge their lists.

Here’s a pseudo-code I thought:

foreach (var item in StaticList)
{
    if (item.Equals(anotherItem)) // i.e., dictionaries are equal
    {
        item.UInt64List.AddRange(anotherItem.UInt64List);
        StaticList.Remove(anotherItem);
    }
}

How can I accomplish this without resorting to features added by the latest frameworks (my target framework is .NET 2.0, so there’s no fancy Union, Intersect, etc.)?

Note: I have already figured out how to check if two dictionaries are equal, I want to find duplicates and merge them.

Answer 1

You have to compare all the items against each other.

for (int i = 0; i < StaticList.Length-1; i++)
{
    var item = StaticList[i];
    for (int j = i+1; j < StaticList.Length;)
    {
        var anotherItem = StaticList[j];
        if (item.Equals(anotherItem)) // i.e., dictionaries are equal
        {
            item.UInt64List.AddRange(anotherItem.UInt64List);
            StaticList.RemoveAt(j); // it has better performance compared to `StaticList.Remove(anotherItem);`
        }
        else
            j++;
    }
}

I do not recommend using a foreach loop, because you cannot modify the list during iteration and you have to put items in another list and remove them later, which imposes a lot of performance penalty to store items and to search later to remove.