Question

I’m looking for a way to get distinct values from a jagged array. I’ve tried putting it in a dictionary, but it doesn’t seem to see the values as distinct. Anyone any ideas for a solution? Here is what I have so far:

int[][] connectionList = GetArray();

Sample data returned from this:

[0][1, 130, 136, 138]
[1][1, 78, 126, 138]
[2][1, 10, 125, 138]
[3][1, 130, 136, 138]
[4][1, 78, 126, 138]
[5][1, 130, 136, 138]
[6][1, 72, 135, 138]
[7][1, 73, 135, 138]
[8][1, 130, 136, 138]

Have tried adding to a dictionary. I tried to catch duplicate values as they are added, but that didn’t work, so tried to add .Distinct(), but no joy there either

Dictionary<int, int[]> myDictionary = new Dictionary<int, int[]>();
for (int i = 0; i < connectionList.Length; i++)
{ 
    List<int> list = new List<int>();
    for (int j = 0; j < connectionList[i].Length; j++)
    {
        list.Add(connectionList[i][j]);        
    }
    if (myDictionary.Where(x => x.Value == list.ToArray()).Count() == 0)
        myDictionary.Add(i, list.ToArray());
}
var distinctList = myDictionary.Values.Distinct().ToList();

From the above list, the output I’m looking for would be:

[0][1, 130, 136, 138]
[1][1, 78, 126, 138]
[2][1, 10, 125, 138]
[4][1, 72, 135, 138]
[5][1, 73, 135, 138]

Any thoughts how I could achieve this?

Answer 1

Here’s one way to do it:

var distinctList = connectionList.GroupBy(x => string.Join(",", x))
                                 .Select(g => g.First())
                                 .ToList();

Although it’s probably preferable to create a custom IEqualityComparer<T> — as suggested by Crab Bucket and Tobias — rather than creating a throwaway string to use for the comparison.