Hi I have allLists that contains lists of string I want to find common items among these string lists i have tried
var intersection = allLists
.Skip(1)
.Aggregate(
new HashSet<string>(allLists.First()),
(h, e) => { h.IntersectWith(e); return h);`
and also intersection ( hard code lists by index) all of them did not work when I tried
var inter = allLists[0].Intersect(allLists[1]).Intersect(allLists[2])
.Intersect(allLists[3]).ToList();
foreach ( string s in inter) Debug.WriteLine(s+"\n ");
So how am I going to do this dynamically and get common string items in the lists; is there a way to avoid Linq?
I'd do it like this:
class Program
{
static void Main(string[] args)
{
List<string>[] stringLists = new List<string>[]
{
new List<string>(){ "a", "b", "c" },
new List<string>(){ "d", "b", "c" },
new List<string>(){ "a", "e", "c" }
};
// Will contian only 'c' because it's the only common item in all three groups.
var commonItems =
stringLists
.SelectMany(list => list)
.GroupBy(item => item)
.Select(group => new { Count = group.Count(), Item = group.Key })
.Where(item => item.Count == stringLists.Length);
foreach (var item in commonItems)
{
Console.WriteLine(String.Format("Item: {0}, Count: {1}", item.Item, item.Count));
}
Console.ReadKey();
}
}
An item is a common item if it occurs in all groups hence the condition that its count must be equal to the number of groups:
.Where(item => item.Count == stringLists.Length)
EDIT:
I should have used the HashSet like in the question. For lists you can replace the SelectMany line with this one:
.SelectMany(list => list.Distinct())
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