How can you sort an array by the number of most repeated values?

Question

C++ / C#

For example, there is a sorted array array:
1
1
1
2
3
3
4
4
4
4
5
6
6
7
8
So here's how to sort the array by the number of most repeated values:
4
4
4
4
1
1
1
6
6
3
3
8
7
5
2

Answer 1

int[] array = {1, 1, 1, 2, 3, 3, 4, 4, 4, 4, 5, 6, 6, 7, 8};
var sortedByFrequency = array
    .GroupBy(o => o)
    .OrderByDescending(o => o.Count())
    .ThenByDescending(o => o.Key)
    .SelectMany(o => o)
    .ToArray();
Console.WriteLine(string.Join(",",sortedByFrequency.Select(o => o.ToString())));
//4,4,4,4,1,1,1,6,6,3,3,8,7,5,2

It if in one LINQ expression. If you need something very fast for large input arrays, then you should look for something else.