Check if one list contains all items from another list in order

Question

How can I determine if List A contains all of the elements from List B in the same order?

List A can have additional elements that List B does not have, but must co

Answer 1

Use String.Join() to concat ListA elements together. Then use it again to concat ListB elements together. Then use ConcatListA.IndexOf(ConcatListB).

Answer 2

I think my version is more efficient.

public static class CollectionExtension
{
    public static bool SequenceContain<T>(this IEnumerable<T> target, IEnumerable<T> that)
    {
        var targetEnumerater = target.GetEnumerator();
        var thatEnumerater = that.GetEnumerator();
        var thatHasValue = thatEnumerater.MoveNext();
        var targetHasValue = targetEnumerater.MoveNext();
        var matchCount = 0;
        try
        {
            while (thatHasValue && targetHasValue)
            {
                if (!EqualityComparer<T>.Default.Equals(targetEnumerater.Current, thatEnumerater.Current))
                {
                    if (matchCount > 0)
                    {
                        thatEnumerater.Reset();
                        thatEnumerater.MoveNext();
                        matchCount = 0;
                    }
                    targetHasValue = targetEnumerater.MoveNext();
                    continue;
                }
                targetHasValue = targetEnumerater.MoveNext();
                thatHasValue = thatEnumerater.MoveNext();
                matchCount++;
            }
            return matchCount == that.Count();
        }
        finally
        {
            thatEnumerater.Dispose();
            targetEnumerater.Dispose();
        }
    }
}

Answer 3

This takes each part of ListA and compares it with ListB with SequenceEqual:

bool containsSameSequence = ListA
    .Where((item, index) => index <= ListA.Count - ListB.Count)
    .Select((item, index) => ListA.Skip(index).Take(ListB.Count))
    .Any(part => part.SequenceEqual(ListB));

Demo

It returns true on the first matching sequence.

Answer 4

Here's a quick way:

var equal = listA.Count - listB.Count < 0 
    ? false 
    : Enumerable.Range(0, listA.Count - listB.Count).Any(i => 
      listA.Skip(i).Take(listB.Count).SequenceEqual(listB));

---

However, I'd prefer to use an extension method like this:

public static bool ContainsSequence<T>(this IEnumerable<T> outer, 
                                       IEnumerable<T> inner)
{
    var innerCount = inner.Count();
    for(int i = 0; i < outer.Count() - innerCount; i++)
    {
        if(outer.Skip(i).Take(innerCount).SequenceEqual(inner))
            return true;
    }

    return false;
 }

which you can call like:

var equals = listA.ContainsSequence(listB);

---

And here's a more efficient version of the same extension method specific to List<T>:

public static bool ContainsSequence<T>(this List<T> outer, List<T> inner)
{
    var innerCount = inner.Count;

    for (int i = 0; i < outer.Count - innerCount; i++)
    {
        bool isMatch = true;
        for (int x = 0; x < innerCount; x++)
        {
            if (!outer[i + x].Equals(inner[x]))
            {
                isMatch = false;
                break;
            }
        }

        if (isMatch) return true;
    }

    return false;
}