I have a List<>
that contains a List<string>
, of which I need to determine the unique count from the List<string
, and order by the frequency of the count.
Example:
This would output (rank / combination / frequency)
I can come up with a brute-force approach but can this be done more elegantly with LINQ? This isn't exactly a Cartesian approach from what I can tell.
Thanks.
You could write your own IEqualityComparer
and use it with GroupBy
.
public class StringArrayValueComparer : IEqualityComparer<List<string>>
{
public bool Equals(List<string> x, List<string> y)
=> x.SequenceEqual(y);
public int GetHashCode(List<string> obj)
=> obj.Aggregate(1, (current, s) => current * 31 + s.GetHashCode());
}
var list = new List<List<string>>(new[]
{
new List<string>(new [] { "a", "b", "c" }),
new List<string>(new [] { "d", "e", "f" }),
new List<string>(new [] { "a", "b" }),
new List<string>(new [] { "a", "b", "c" }),
new List<string>(new [] { "a", "b", "c" }),
new List<string>(new [] { "a", "b" })
});
var orderedList = list
.GroupBy(x => x, x => x, (x, enumerable) => new { Key = x, Count = enumerable.Count()}, new StringArrayValueComparer())
.OrderByDescending(x => x.Count)
.Select((x, index) => new { Rank = index + 1, Combination = x.Key, Frequency = x.Count });
foreach (var entry in orderedList)
{
Console.WriteLine($"{entry.Rank} - {string.Join(",", entry.Combination)} - {entry.Frequency}");
}
1 - a,b,c - 3
2 - a,b - 2
3 - d,e,f - 1
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