使用分隔符序列拆分ICollection<T>

Question

这是针对C# 3.5的

我尝试将ICollection拆分为单独的ICollections，其中的分隔符是一个序列。

例如

ICollection<byte> input = new byte[] { 234, 12, 12, 23, 11, 32, 23, 11 123, 32 };
ICollection<byte> delimiter = new byte[] {23, 11};
List<IICollection<byte>> result = input.splitBy(delimiter);

会导致

result.item(0) = {234, 12, 12};
result.item(1) = {32};
result.item(2) = {123, 32};

Answer 1

private static IEnumerable<IEnumerable<T>> Split<T>
    (IEnumerable<T> source, ICollection<T> delimiter)
{
    // window represents the last [delimeter length] elements in the sequence,
    // buffer is the elements waiting to be output when delimiter is hit

    var window = new Queue<T>();
    var buffer = new List<T>();

    foreach (T element in source)
    {
        buffer.Add(element);
        window.Enqueue(element);
        if (window.Count > delimiter.Count)
            window.Dequeue();

        if (window.SequenceEqual(delimiter))
        {
            // number of non-delimiter elements in the buffer
            int nElements = buffer.Count - window.Count;
            if (nElements > 0)
                yield return buffer.Take(nElements).ToArray();

            window.Clear();
            buffer.Clear();
        }
    }

    if (buffer.Any())
        yield return buffer;
}

Answer 2

最佳解决方案不是使用SequenceEqual()来检查每个子范围，否则您可能会为序列中的每个项目迭代分隔符的长度，这可能会影响性能，特别是对于较大的分隔符序列。可以在枚举源序列时对其进行检查。

这是我要写的，但总有改进的空间。我的目标是拥有与String.Split()相似的语义。

public enum SequenceSplitOptions { None, RemoveEmptyEntries }
public static IEnumerable<IList<T>> SequenceSplit<T>(
    this IEnumerable<T> source,
    IEnumerable<T> separator)
{
    return SequenceSplit(source, separator, SequenceSplitOptions.None);
}
public static IEnumerable<IList<T>> SequenceSplit<T>(
    this IEnumerable<T> source,
    IEnumerable<T> separator,
    SequenceSplitOptions options)
{
    if (source == null)
        throw new ArgumentNullException("source");
    if (options != SequenceSplitOptions.None
     && options != SequenceSplitOptions.RemoveEmptyEntries)
        throw new ArgumentException("Illegal option: " + (int)option);
    if (separator == null)
    {
        yield return source.ToList();
        yield break;
    }

    var sep = separator as IList<T> ?? separator.ToList();
    if (sep.Count == 0)
    {
        yield return source.ToList();
        yield break;
    }

    var buffer = new List<T>();
    var candidate = new List<T>(sep.Count);
    var sindex = 0;
    foreach (var item in source)
    {
        candidate.Add(item);
        if (!item.Equals(sep[sindex]))
        {   // item is not part of the delimiter
            buffer.AddRange(candidate);
            candidate.Clear();
            sindex = 0;
        }
        else if (++sindex >= sep.Count)
        {   // candidate is the delimiter
            if (options == SequenceSplitOptions.None || buffer.Count > 0)
                yield return buffer.ToList();
            buffer.Clear();
            candidate.Clear();
            sindex = 0;
        }
    }
    if (candidate.Count > 0)
        buffer.AddRange(candidate);
    if (options == SequenceSplitOptions.None || buffer.Count > 0)
        yield return buffer;
}

Answer 3

以下是我对此的看法：

public static IEnumerable<IList<byte>> Split(IEnumerable<byte> input, IEnumerable<byte> delimiter)
{
    var l = new List<byte>();
    var set = new HashSet<byte>(delimiter);
    foreach (var item in input)
    {
        if(!set.Contains(item))
            l.Add(item);
        else if(l.Count > 0)
        {
            yield return l;
            l = new List<byte>();
        }
    }
    if(l.Count > 0)
        yield return l;
}