I could use the following linq expression to count the number of occurrences of a word as follows:
string test = "And And And";
int j = test.Split(' ').Count(x => x.Contains("And"));
However what if I was searching for "And And", Is there a way to use linq to count words without using split. Do any of these methods take longer the O(n)?
You can use a regular expression:
string test = "And And And";
int j = Regex.Matches(test, "And").Cast<Match>().Count();
BTW, do you want to allow overlapping occurrences? i.e. if you're looking for "And And", do you consider that test contains 1 or 2 occurrences of it?
MatchCollection implements the non-generic IEnumerable, but not IEnumerable<Match>, and Count only works on the generic version.
Cast. Thanks @ThomasLevesqueI found a clever solution that can be resolved serverside with most LINQ to ORMs:
string search = "foo";
int searchLength = search.Length;
var result = qry.Select(i => new { Object = i, Occurrences = (i.SomeProperty.Length - i.SomeProperty.Replace(search, "").Length) / searchLength });
The idea is to replace the substring by an empty string and then divide the difference in string length by the length of the search term.
You can use IndexOf:
string what = "And";
int count = 0;
int pos = -what.Length;
for (;;)
{
pos = input.IndexOf(what, pos + what.Length);
if (pos == -1) break;
count++;
}
This is not quite Linq, but you can also make an extension method like below. It is probably more efficient than any Linq solution:
public static int CountSubStrings(this string input, string delimiter, bool ignoreCase = false)
{
int instancesNo = 0;
int pos = 0;
while((pos = input.IndexOf(delimiter, pos, ignoreCase ? StringComparison.InvariantCultureIgnoreCase : StringComparison.InvariantCulture)) != -1)
{
pos += delimiter.Length;
instancesNo++;
}
return instancesNo;
}
int j = test.Split(' ').Count(x => x == "And");?