How to get range key of specific value in sortedList

Question

I want to get range keys from sortedlist or other similar sorted data structure.

for example ;

                SortedList<long, string> testSorted = new SortedList<long, string>();
                testSorted.Add(1, "a");
                testSorted.Add(4, "b");
                testSorted.Add(15, "c");

                testSorted.Add(12, "d");
                testSorted.Add(10, "e");
                testSorted.Add(8, "f");

                int wantspecifickey = 7;

                int index = testSorted.GetClosestIndex(wantspecifickey);
                int range = 1;
                List<long> rangeIndex = testSorted.GetRangeIndexKey(index , range);

The key value closest to 7 is 8.

So the index value is 2.

After that, at index 2 (key: 8), the keys of the index within index range 1 are 4 8 and 10.

Do you guys any good idea to solve my problem?

PS. I don't have to use sortedlist. If there is a more efficient data structure, please let me know too.

Answer 1

Here is my two cents;

public class Program
{
    public static Tuple<int, int, int> FindClosestRange(int[] keys, int key)
    {
        if (keys == null)
            throw new ArgumentNullException(nameof(keys));
        if (keys.Length == 0)
            throw new ArgumentException();
        
        Array.Sort(keys);
        var minDiff = int.MaxValue;
        var minIndex = 0;
        for(var index = 0; index < keys.Length;index++)
        {
            var diff = Math.Abs(keys[index] - key);
            if (diff < minDiff)
            {
                minDiff = diff;
                minIndex = index;
            }
        }
        var lowerBoundry = Math.Max(minIndex - 1, 0);
        var higherBoundry = Math.Min(minIndex + 1, keys.Length - 1);
        
        return Tuple.Create(keys[lowerBoundry], keys[minIndex], keys[higherBoundry]);
    }
    
    public static void Main()
    {
        var list = new Dictionary<int, string>()
        {
            { 1, "a" },
            { 4, "b" },
            {10, "e"},
            { 15, "c" },
            {8, "f"},
            { 12, "d"},
        };

        var range = FindClosestRange(list.Keys.ToArray(), 7);
        Console.WriteLine($"Closest {range}");
    }
}

It doesn't use sorted list but uses dictionary.