Can you reverse order a string in one line with LINQ or a LAMBDA expression

Question

Not that I would want to use this practically (for many reasons) but out of strict curiousity I would like to know if there is a way to reverse order a string using LINQ and/or LAMBDA expressions in one line of code, without utilising any framework "Reverse" methods.

e.g.

string value = "reverse me";
string reversedValue = (....);

and reversedValue will result in "em esrever"

EDIT Clearly an impractical problem/solution I know this, so don't worry it's strictly a curiosity question around the LINQ/LAMBDA construct.

Solution 1

I don't see a practical use for this but just for the sake of fun:

new string(Enumerable.Range(1, input.Length).Select(i => input[input.Length - i]).ToArray())

Solution 2

Well, I can do it in one very long line, even without using LINQ or a lambda:

string original = "reverse me"; char[] chars = original.ToCharArray(); char[] reversed = new char[chars.Length]; for (int i=0; i < chars.Length; i++) reversed[chars.Length-i-1] = chars[i]; string reversedValue = new string(reversed);

(Dear potential editors: do not unwrap this onto multiple lines. The whole point is that it's a single line, as per the sentence above it and the question.)

However, if I saw anyone avoiding using framework methods for the sake of it, I'd question their sanity.

Note that this doesn't use LINQ at all. A LINQ answer would be:

string reverseValue = new string(original.Reverse().ToArray());

Avoiding using Reverse, but using OrderByDescending instead:

string reverseValue = new string(original.Select((c, index) => new { c, index })
                                         .OrderByDescending(x => x.index)
                                         .Select(x => x.c)
                                         .ToArray());

Blech. I like Mehrdad's answer though. Of course, all of these are far less efficient than the straightforward approach.

Oh, and they're all wrong, too. Reversing a string is more complex than reversing the order of the code points. Consider combining characters, surrogate pairs etc...

Solution 3

new string(value.Reverse().ToArray())

Solution 4

var reversedValue = value.ToCharArray()
                         .Select(ch => ch.ToString())
                         .Aggregate<string>((xs, x) => x + xs);

Solution 5

Variant with recursive lambda:

  var value = "reverse me";
  Func<String, String> f = null; f = s => s.Length == 1 ? s : f(s.Substring(1)) + s[0]; 
  var reverseValue = f(value);

LP, Dejan

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