Reversing Arrays, Array.Reverse()

Question

I have the following code to reverse a string:

Console.Title = "*****Reverse a String*****";
Console.WriteLine("*****Reverse a String*****");
Console.WriteLine("=> Enter the text to be reversed:");
string input = Console.ReadLine();
Console.WriteLine("=> Reversing...");
char[] arrInput = input.ToCharArray();
Array.Reverse(arrInput);
String final = new String(arrInput);
Console.WriteLine("=> {0}", final);
Console.WriteLine("=> Press any key to terminate.");
Console.ReadKey();

Array.Reverse(arrInput) works but arrInput.Reverse() doesnt! Any pointers?

Selman Genç · Accepted Answer · 2014-12-31 00:00:46Z

5

arrInput.Reverse uses LINQ Reverse method which doesn't change the original collection. You need to call ToArray on it

var reversed = arrInput.Reverse().ToArray();

answered Dec 31, 2014 at 0:00

Selman Genç

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1 Comment

user4264492 Over a year ago

Thanks! Will select as answer when it lets me!

Kevin DiTraglia · Accepted Answer · 2014-12-31 00:06:55Z

1

arrInput.Reverse() returns an enumerable:

IEnumerable<char> inputEnumerable = arrInput.Reverse();

Also as Selman22 points out, Reverse() is going to return an IEnumerable not an array, so you'll also have to add ToArray() if you want to use the original variable:

arrInput = arrInput.Reverse().ToArray();

edited Dec 31, 2014 at 0:06

answered Dec 31, 2014 at 0:00

Kevin DiTraglia

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Kevin DiTraglia Over a year ago

@Selman22 Good point, I was thinking the array could hold an IEnumerable for some reason

littlerufe · Accepted Answer · 2015-01-01 17:43:49Z

0

You don't have to explicitly create an array to use the Reverse method; you could just do this:

// Get string from user as you're already doing
string input = Console.ReadLine();

// Reverse it and assign to new string
string reversed = new string(input.Reverse().ToArray());

In other words, this code:

string input = Console.ReadLine();
Console.WriteLine("=> Reversing...");
char[] arrInput = input.ToCharArray();
Array.Reverse(arrInput);
String final = new String(arrInput);

Can be simplified to:

string input = Console.ReadLine();
Console.WriteLine("=> Reversing...");
String final = new String(input.Reverse().ToArray());

edited Jan 1, 2015 at 17:43

answered Dec 31, 2014 at 0:21

littlerufe

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3 Comments

user4264492 Over a year ago

Wouldn't .ToArray() make it an array which would make it an array when reversed is a string?

littlerufe Over a year ago

@LukeParker Not really; Reverse is called first, which returns an IEnumerable<char>. The ToArray() call is needed to convert the IEnumerable to an Array type for the string constructor. But you can call Reverse on a string without converting it to an Array, like: var reversed = "some String".Reverse();. Just as you can grab a character from a string using an index without explicitly converting it to an array: char fourthCharacter = "someString"[3];

littlerufe Over a year ago

Updated answer with how the explicit array declaration can be removed, hope that helps.

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