Split a list into multiple lists at increasing sequence broken

Question

I\'ve a List of int and I want to create multiple List after splitting the original list when a lower or same number is found. Numbers are not in sorted order.<

Answer 1

I'd just go for something simple:

public static IEnumerable> SplitWhenNotIncreasing(List numbers)
{
    for (int i = 1, start = 0; i <= numbers.Count; ++i)
    {
        if (i != numbers.Count && numbers[i] > numbers[i - 1])
            continue;

        yield return numbers.GetRange(start, i - start);
        start = i;
    }
}

Which you'd use like so:

List data = new List { 1, 2, 1, 2, 3, 3, 1, 2, 3, 4, 1, 2, 3, 4, 5, 6 };

foreach (var subset in SplitWhenNotIncreasing(data))
    Console.WriteLine(string.Join(", ", subset));

---

If you really did need to work with IEnumerable, then the simplest way I can think of is like this:

public sealed class IncreasingSubsetFinder where T: IComparable
{
    public static IEnumerable> Find(IEnumerable numbers)
    {
        return new IncreasingSubsetFinder().find(numbers.GetEnumerator());
    }

    IEnumerable> find(IEnumerator iter)
    {
        if (!iter.MoveNext())
            yield break;

        while (!done)
            yield return increasingSubset(iter);
    }

    IEnumerable increasingSubset(IEnumerator iter)
    {
        while (!done)
        {
            T prev = iter.Current; 
            yield return prev;

            if ((done = !iter.MoveNext()) || iter.Current.CompareTo(prev) <= 0)
                yield break;
        }
    }

    bool done;
}

Which you would call like this:

List data = new List { 1, 2, 1, 2, 3, 3, 1, 2, 3, 4, 1, 2, 3, 4, 5, 6 };

foreach (var subset in IncreasingSubsetFinder.Find(data))
    Console.WriteLine(string.Join(", ", subset));