Regex for positive integers separated by abritrary space

Question

Example input: " 1 4 2 5 9 "

Wanted: "1", "4", "2", "5", "9"

Use like

var rgx = new Regex("???"); 
var matches = rgx.Matches("  1  4 2 5 9 ");
var nums = new List<int>();
foreach(var match in matches)
    nums.Add(match.Caputre.Value);

Why regex? Do the strings always consist of digit chunks and whitespace only? — Wiktor Stribiżew, Aug 17 '16 at 15:13
@WiktorStribiżew If you have a better suggestion than using regex here, please let me know. Simply, what I need is to parse integers out of a string of integers separated by arbitrary amounts of whitespace. — user6048670, Aug 17 '16 at 15:14
Do you mean any whitespace or literal spaces (as your example shows)? — Wiktor Stribiżew, Aug 17 '16 at 15:16
Split() on " " with StringSplitOptions.RemoveEmptyEntries set? — Alex K., Aug 17 '16 at 15:17
Are they always single digits? If so you could do something like: " 1 2 9 3".Where(c => char.IsDigit(c)).ToList(); — EJoshuaS - Stand with Ukraine, Aug 17 '16 at 15:32

Wiktor Stribiżew · Accepted Answer · 2016-08-17T15:23:43.230

If you are sure there are only spaces and digit chunks, you can use LINQ and parse integers with int.Parse:

var str = "  1  4 2 5 9 ";
var res = str.Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries)
     .Select(r => int.Parse(r))
     .ToList();

If you also need a kind of a pre-validation (to make sure your string only contains any whitespace and digit chunks, you may use a safer regex based solution:

var res2 = Regex.Matches(str, @"^(?:\s*([0-9]+))+\s*$")
    .Cast<Match>()
    .SelectMany(p => p.Groups[1].Captures.Cast<Capture>().Select(m => int.Parse(m.Value)))
    .ToList();

Both result in:

score 0 · Answer 2 · 2016-08-17T16:00:27.437

Split would be a slower way to do it.

Try using matches(), something like:

var nums = new List<int>();
foreach (Match match in Regex.Matches("  1  4 2 5 9 ", @"\d+"))
{
    nums.Add(Int32.Parse(match.Value));
}

///////////////
StringBuilder builder = new StringBuilder();
foreach (int nN in nums)
{
    builder.Append(nN).Append(",");
}
string result = builder.ToString();
Console.WriteLine("{0}", result);

Regex for positive integers separated by abritrary space

2 Answers2