Extract number at end of string in C#

Question

Probably over analysing this a little bit but how would stackoverflow suggest is the best way to return an integer that is contained at the end of a string.

Thus far I have considered using a simple loop, LINQ and regex but I'm curious what approaches I'll get from the community. Obviously this isn't a hard problem to solve but could have allot of variance in the solutions.

So to be more specific, how would you create a function to return an arbitrarily long integer/long that is appended at the end of an arbitrarily long string?

CPR123 => 123 ABCDEF123456 => 123456 

Answer 1

Use this regular expression:

\d+$  var result = Regex.Match(input, @"\d+$").Value; 

or using Stack, probably more efficient:

var stack = new Stack<char>();  for (var i = input.Length - 1; i >= 0; i--) {     if (!char.IsNumber(input[i]))     {         break;     }      stack.Push(input[i]); }  var result = new string(stack.ToArray()); 

Answer 2

Obligatory LINQ one-liner

var input = "ABCD1234"; var result = string.Concat(input.ToArray().Reverse().TakeWhile(char.IsNumber).Reverse());