I am getting back a "string[]" from a 3rd party library. I want to do a contains on it. what is the most efficient way of doing this?
Add a comment
|
6 Answers
Array.IndexOf:
bool contains = Array.IndexOf(arr, value) >= 0;
Or just use LINQ:
bool contains = arr.Contains(value);
LINQ should be "fast enough" for most purposes.
Comments
If you are only checking a single time, use Array.IndexOf or the LINQ Contains method like Marc proposed. If you are checking several times, it might be faster to first convert the string array into a HashSet<string>.
1 Comment
Marc Gravell
Good catch with HashSet; +1 ;-p
Unless you know the String array is sorted by a particular order the most efficient thing you can do is linear algorithm (i.e. compare each string in the array until you find a match or the end of the array.
If the array is sorted a binary search is much faster.
Another way to optimize the algorithm (although the complexity is not reduced) is to vectorize the string comparisons.
Comments
I'm fairly certain that a for loop is faster, if absolute speed is your concern. I.e.,
for (int i = 0; i < arr.Length; ++i)
if (arr[i] == value) return true;
return false;
Comments
If you're searching once or twice, use a linear search or IndexOf.
If you're searching a few times, put the strings into a HashSet.
If you're searching zillions of times in a time-critical fashion, use a HashSet and manage its bucket count yourself.
Comments
You can use the IEnumerable.Foreach Custom Extension
public static class CollectionExtensions
{
public static void ForEach<T>(this IEnumerable list, Action<T> action)
{
foreach (T item in list)
{
action(item);
}
}
}
class Program
{
static void Main(string[] args)
{
String[] list = new String[] { "Word1", "Word2", "Word3" };
list.ForEach<String>(p => Console.WriteLine(p));
list.ForEach(delegate(String p) { Console.WriteLine(p); });
}
}
Hope this help's.
