Say I have the following 2 arrays
string[] keys = new string[]{"Annalee Call","Bishop","Ash"};
MyClass[] vals = new MyClass[]{
new MyClass(){name = "Ash"},
new MyClass(){name = "Annalee Call"},
new MyClass(){name = "Bishop"}
};
What is the best way to sort the MyClass array by name based on the keys array without resorting to for loops?
One way to do it would be as follows:
var sorted = vals.OrderBy(s => Array.IndexOf(keys, s.name)).ToArray();
Note that this algorithm is asymptotically very slow: it has O(N^2*LogN) complexity. To bring it back to the "normal" O(N*LogN), prepare a lookup dictionary for finding indexes, like this:
var keyDict = keys.Select((v,i)=>new {v,i}).ToDictionary(p=>p.v, p=>p.i);
var sorted = vals.OrderBy(s => keyDict[s.name]).ToArray();
I would use this approach to do the sorting. It handles the case if values in vals are missing from the keys list.
var rank =
keys
.Select((v, n) => new { Value = v, Rank = n, })
.ToLookup(vn => vn.Value, vn => vn.Rank);
var query =
from v in vals
orderby rank[v.name]
.DefaultIfEmpty(int.MaxValue)
.First()
select v;
Otherwise it is very similar to dasblinkenlight's answer.
