How sort Dictionary by 2 criterias and subcriteria in c#

Question

I want to sort myDictionary first by Key and then by Value.

Dictionary<int, double> myDictionary = new Dictionary<int, double>()
{
    {1,514},
    {2,509},
    {3,510},
    {4,509},
    {5,517},
    {6,512},
    {7,514},
    {8,511}
}

I need to find min and max Value, then to sort it by Key.

var orderedDict = myObjectDictionary
       .OrderByDescending(a => a.Value)
       .ThenBy(b => b.Key);

But I need to find this object with min Value farthest(using Key) from object with max Value. If there is two object with min/max Value to get farthest(using Key) one from opposite object(min/max).

After that I need to look for object near to min/max and if their Values are near to min/max Values and they are farthest to get them.

In this case: Max= 5, 517 Min= 3, 510

other ways to get max value https://stackoverflow.com/questions/10290838/how-to-get-max-value-from-dictionary — demo, Sep 21 '21 at 14:41
@PeterCsala my question is how can i achive this result (In this case: Max= 5, 517 Min= 3, 510)? Can someone provide a code example or somethin to show? — Hristo Ivanov, Sep 23 '21 at 05:40
I can see that 517 is the largest value, that's why 5, 517 is the max. But there are two 509 values at key 2 and 4. So why is 3, 510 is your min? — Peter Csala, Sep 23 '21 at 05:53
Because i can not get min and max if they are next to each other. — Hristo Ivanov, Sep 24 '21 at 05:44

score 0 · Accepted Answer · answered Sep 24 '21 at 07:55

Requirement: Can't get a min and a max if they are next to each other.

In the following solution I've assumed that myDictionary keys are incremented by 1.

You can have the desired output with the following code:

var groupedByValues = myDictionary.ToLookup(p => p.Value, p => p.Key);

var orderByValues = from item in groupedByValues
                    orderby item.Key ascending
                    select (Value:item.Key, Indexes: item.ToList());
var orderedByValues = orderByValues.ToList();

var maxCandidates = orderByValues.Last();
(int Key, double Value) max = (maxCandidates.Indexes.First(), maxCandidates.Value);
(int Key, double Value)? min = null;

foreach(var item in orderedByValues)
{
    if (item.Indexes.Any(idx => Math.Abs(idx - max.Key) == 1))
        continue;
    else
    {
        min = (item.Indexes.First(), item.Value);
        break;
    }
};

var groupedByValues = myDictionary.ToLookup(p => p.Value, p => p.Key);

Here we create groups based on the value, the groupedByValues looks like this:

var orderByValues = from item in groupedByValues
                    orderby item.Key ascending
                    select (Value:item.Key, Indexes: item.ToList());

var orderedByValues = orderByValues.ToList();

Here we simply order the previous collection by its keys
The orderByValues is just a query, the orderedByValues is its materialized form:

var maxCandidates = orderByValues.Last();
(int Key, double Value) max = (maxCandidates.Indexes.First(), maxCandidates.Value);
(int Key, double Value)? min = null;

By issuing the orderByValues.Last command we get the highest value
- The highest value can be present multiple times that's why we have Indexes
- I've picked the first index from Indexes but you might need to alter this logic based on your requirements
We convert the maxCandidates into the expected output format
We create a min variable, which is nullable to be able to initialize it

foreach(var item in orderedByValues)
{
    if (item.Indexes.Any(idx => Math.Abs(idx - max.Key) == 1))
        continue;
    else
    {
        min = (item.Indexes.First(), item.Value);
        break;
    }
};

Here we iterate through the orderedByValues collection in order to find the first min which satisfies all requirements
We are checking the distance between the max Key and the min candidate's indexes
- If any of the indexes is next to the max key, then we continue searching
- If none of the indexes is next to the max key, then we have found the min

How sort Dictionary by 2 criterias and subcriteria in c#

1 Answers1