how to get the rank list of multiple number in a list using C#?

Question

I have the following list in C#:

List<double> arr = new List<double> { 5, 10, 7, 15, 9, 21, 1 };

I want store their ranks in another list for example List<double> rank. Finally I want get the following:

6 3 5 2 4 1 7

How can I do this?

Answer 1

List<double> arr = new List<double> { 5, 10, 7, 15, 9, 21, 1 };

var rankDict = arr.Distinct().OrderByDescending(num=>num)
    .Select((number, index) => new {Number = number, Rank = index})
    .ToDictionary(m => m.Number, m => m.Rank);

var rankedArray = new List<double>();

foreach(var num in arr)
{
    rankedArray.Add(rankDict[num] + 1);
}

Console.WriteLine(string.Join("-", rankedArray));

Fiddle - https://dotnetfiddle.net/7C5o52