CODEWITHSUNDEEP
c#.netlinq
eugeneK
eugeneK

Reputation: 11116

List contains in List check

I have a IEnumerable<Object> a with 6 items in chronological order in it. I want to test if list IEnumerable<Object> b with 3 items in chronological order.

IEnumerable<Object> a item values: a,b,c,d,f,g

IEnumerable<Object> b item values: b,d,f

Is it possible to be done with LINQ ?

Upvotes: 4

Views: 157

Answers (3)

Daniel Hilgarth
Daniel Hilgarth

Reputation: 174309

The one liner approach of Rawling and Tim is very nice, but it has one little gotcha: b is iterated twice.
If that is a problem for you, you could use an iterator based approach. This can be created as an extension method:

public static bool IsContainedWithinInOrder<T>(this IEnumerable<T> values,
                                               IEnumerable<T> reference)
{
    using(var iterator = reference.GetEnumerator())
    {
        foreach(var item in values)
        {
            do
            {
                if(!iterator.MoveNext())
                    return false;
            } while(!Equals(iterator.Current, item));
        }

        return true;
    }
}

This would iterate both sequences only once and overall is more lightweight. You would call it like this:

b.IsContainedWithinInOrder(a);

Please forgive the name of the method...

Upvotes: 7

Tim Schmelter
Tim Schmelter

Reputation: 460108

I assume that you have two lists and you want to check if the second list item have the same order as the same items in the first list.

Perhaps:

var allSameOrder = list1.Intersect(list2).SequenceEqual(list2);

Demo

Upvotes: 6

Rawling
Rawling

Reputation: 50114

You can use the following:

bool AContainsEverythingInBInTheSameOrder =
    a.Intersect(b).SequenceEquals(b);

a.Intersect(b) returns everything that is in both a and b, in the same order in which it appears in a.

Upvotes: 8

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