0

For example

Input array: 'a', 'b', 'B', 'A'

Output with Array.Sort(): 'A', 'B', 'a', 'b'

Desired output: 'A', 'a', 'B', 'b'

I understand why 'A' is considered lower than 'a', but I want it to be sorted alphabetically, not by the corresponding integers of the characters.

Is there a Comparer class that would solve the problem as a second argument for Array.Sort() ?

L.Z.
  • 11
  • 1
  • Are they `char` elements, or single character strings? – Ron Beyer Oct 03 '18 at 20:38
  • They are char elements, declared like so: char [] charArray = { 'a', 'b', 'B', 'A' }; – L.Z. Oct 03 '18 at 20:40
  • The question is slightly underspecified. Plainly you want `A` and `a` to be both less than `B` and `b` but it is unclear if `a` is smaller than, greater than or equal to `A` in your conception. – Eric Lippert Oct 03 '18 at 21:10

2 Answers2

5

Is there a Comparer class that would solve the problem as a second argument for Array.Sort() ?

For strings, you want to use OrdinalIgnoreCase or InvariantCultureIgnoreCase, depending on whether you care about culture sensitivity or not. See:

Which is generally best to use -- StringComparison.OrdinalIgnoreCase or StringComparison.InvariantCultureIgnoreCase?

For chars, I do not know of a built-in comparer that does that, but it is easy to write your own. See

What is the correct way to compare char ignoring case?

Note that Array.Sort is a mutating sort; if you want a non-mutating sort, then do an OrderBy on ToUpper or ToUpperInvariant. Note that there are pitfalls here; see

How to sort an array of chars alphabetically so that the uppercase and the lowercase version of the same letter are next to each other?

Note also that it is unclear whether your intention is that A and a be equal -- in which case A, a, A would be a legal ordering, since equal things are equal, or whether you still want an ordering within a and A. Again, be careful. If that's what you want then you'll have to do a ThenBy also.

Eric Lippert
  • 647,829
  • 179
  • 1,238
  • 2,067
0

You can use LINQ to create a new char Array with the right order:

var ans = chars.OrderBy(Char.ToUpper).ThenBy(c => c).ToArray();
NetMage
  • 26,163
  • 3
  • 34
  • 55
  • Can you explain why you are doing `c.ToString().ToUpper()` which allocates a new string, and not `char.ToUpper(c)`, which does not? – Eric Lippert Oct 03 '18 at 21:44
  • 2
    I note also that you can eliminate the first lambda entirely: `chars.OrderBy(char.ToUpper)...` – Eric Lippert Oct 03 '18 at 21:45
  • @EricLippert I forgot about `Char.ToUpper` - it seems like legacy code to me, I expect everything to be a method / extension method fluent style. Updated my answer. – NetMage Oct 03 '18 at 22:12