How to order strings which represent int values

Question

I receive an array which I'm not in control of. Sadly, it comes through as a string although all values are always int values.

There is no option to change the array so I have to work with it.

I'd like to sort them but of course, "10" (as a string) comes before "4" (as a string). I understand why.

Without converting the values of the array to int values, is there a way to order the strings as if they were int? I know converting is a better way, but curious as to the option when using string.

In this example, there will not be negative values

My array could be

"10"
"11"
"2"
"4"

but I'd like to show it as

"2"
"4"
"10"
"11"

Why can't you convert them to ints? strings.OrderBy(int.Parse) would be the obvious way to do it. — Lee
– Lee, Commented Feb 22, 2017 at 20:06

René Vogt · Accepted Answer · 2017-02-22 20:36:41Z

2

Yes, you can order them by the length of the string first:

string[] input = /* wherever it comes from */
string[] result = input.OrderBy(s => s.Length).ThenBy(s => s).ToArray();

Note that this is only a theoretical solution for your special interest in "not parsing" and only works if the strings contain no negative values or leading zeros and only the characters '0' - '9' (no special unicode number symbols etc). In productive code you definitely should parse the strings to get proper results, as Servy already correctly pointed out in the comments.

edited Feb 22, 2017 at 20:36

answered Feb 22, 2017 at 20:04

René Vogt

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7 Comments

Servy Over a year ago

According to you "5" is less than "02"

René Vogt Over a year ago

@Servy according to OP the string will be "2" not "02".

Servy Over a year ago

The question says no such thing. It says that they're all integers, that's all.

Martin Smith Over a year ago

@MyDaftQuestions Are the strings guaranteed to be non negative too?

Servy Over a year ago

@MyDaftQuestions The answer isn't correct, and it produces improper results. You should absolutely be parsing the values. That's how you actually get the correct value. That you don't want to do it doesn't change the fact that that is the correct thing for you to do.

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15ee8f99-57ff-4f92-890c-b56153 · Accepted Answer · 2017-02-22 20:06:33Z

2

I'm guessing you mean you have to keep them as strings, not that you're literally forbidden to ever parse them at all:

string[] a = GetArray();

a = a.OrderBy(s => int.Parse(s)).ToArray();

answered Feb 22, 2017 at 20:06

15ee8f99-57ff-4f92-890c-b56153

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4 Comments

MyDaftQuestions Over a year ago

I appreciate this is probably the better answer as it's the better way, but as my question was about understanding my option with strings, I've given a plus 1

15ee8f99-57ff-4f92-890c-b56153 Over a year ago

@MyDaftQuestions Ah, OK. I did say I was just guessing! Cheers.

MyDaftQuestions Over a year ago

It's probably what I'll end up doing, but my question wasn't about it. I'd give another +1 if I could

15ee8f99-57ff-4f92-890c-b56153 Over a year ago

@MyDaftQuestions Oh yeah, not all questions have to be "what's the most respectable boring way to do this in production code". I've written all kinds of weird code just for the sake of it. I wrote a binary adder in Perl once. Talk about useless.

tinstaafl · Accepted Answer · 2017-02-22 20:16:26Z

2

You could try something like this:

int maxStringLength = int.MaxValue.ToString().Length;
string[] a = { "1", "11", "20", "2", "10" };
a = a.OrderBy(x => x.PadLeft(maxStringLength, '0')).ToArray();

If you know how big your numbers are going to be, you can use a more reasonable value for maxStringLength.

answered Feb 22, 2017 at 20:16

tinstaafl

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Comments

bh_earth0 · Accepted Answer · 2024-12-29 21:34:44Z

1

sort integer in string

can sort positive and negatives,
can't handle padded with 0..

i dont know ,which one is faster. "int.Parse() or this one."

 List<int> input = new List<int>(){3,2,1, -3,-2,-1, 0};
 var result = sortInteger_inString(input );

 private static List<string> sortInteger_inString(List<string> numAsString)
 {
   //sort -/+ integer in string
   var numAsString_Pos = numAsString.Where(x => !x.TrimStart().StartsWith("-"))
       .OrderBy(s => s.Length).ThenBy(s => s);  
 
   var numAsString_Neg = numAsString.Where(x => x.TrimStart().StartsWith("-"))
       .OrderByDescending(s => s.Length).ThenByDescending(s => s);
   
   return numAsString_Neg.Concat(numAsString_Pos).ToList();
 }

answered Dec 29, 2024 at 21:34

bh_earth0

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