我试图将一个列表拆分为一系列较小的列表。

我的问题:我的拆分列表功能没有将它们拆分为正确大小的列表。它应该把它们分成大小为30的列表,但它却把它们分成大小为114的列表?

如何让我的函数将一个列表分割成X个大小为30或更小的列表?

public static List<List<float[]>> splitList(List <float[]> locations, int nSize=30) 
{       
    List<List<float[]>> list = new List<List<float[]>>();

    for (int i=(int)(Math.Ceiling((decimal)(locations.Count/nSize))); i>=0; i--) {
        List <float[]> subLocat = new List <float[]>(locations); 

        if (subLocat.Count >= ((i*nSize)+nSize))
            subLocat.RemoveRange(i*nSize, nSize);
        else subLocat.RemoveRange(i*nSize, subLocat.Count-(i*nSize));

        Debug.Log ("Index: "+i.ToString()+", Size: "+subLocat.Count.ToString());
        list.Add (subLocat);
    }

    return list;
}

如果我在144大小的列表上使用该函数,那么输出是:

指数:4,尺寸:120 指数:3,尺寸:114 指数:2,尺寸:114 指数:1,尺寸:114 索引:0,大小:114


当前回答

我有一个通用的方法,将采取任何类型包括浮动,它已经过单元测试,希望它有帮助:

    /// <summary>
    /// Breaks the list into groups with each group containing no more than the specified group size
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="values">The values.</param>
    /// <param name="groupSize">Size of the group.</param>
    /// <returns></returns>
    public static List<List<T>> SplitList<T>(IEnumerable<T> values, int groupSize, int? maxCount = null)
    {
        List<List<T>> result = new List<List<T>>();
        // Quick and special scenario
        if (values.Count() <= groupSize)
        {
            result.Add(values.ToList());
        }
        else
        {
            List<T> valueList = values.ToList();
            int startIndex = 0;
            int count = valueList.Count;
            int elementCount = 0;

            while (startIndex < count && (!maxCount.HasValue || (maxCount.HasValue && startIndex < maxCount)))
            {
                elementCount = (startIndex + groupSize > count) ? count - startIndex : groupSize;
                result.Add(valueList.GetRange(startIndex, elementCount));
                startIndex += elementCount;
            }
        }


        return result;
    }

其他回答

我发现公认的答案(Serj-Tm)是最健壮的,但我想建议一个通用版本。

public static List<List<T>> splitList<T>(List<T> locations, int nSize = 30)
{
    var list = new List<List<T>>();

    for (int i = 0; i < locations.Count; i += nSize)
    {
        list.Add(locations.GetRange(i, Math.Min(nSize, locations.Count - i)));
    }

    return list;
}
public static List<List<float[]>> SplitList(List<float[]> locations, int nSize=30)  
{        
    var list = new List<List<float[]>>(); 

    for (int i = 0; i < locations.Count; i += nSize) 
    { 
        list.Add(locations.GetRange(i, Math.Min(nSize, locations.Count - i))); 
    } 

    return list; 
} 

通用版:

public static IEnumerable<List<T>> SplitList<T>(List<T> locations, int nSize=30)  
{        
    for (int i = 0; i < locations.Count; i += nSize) 
    { 
        yield return locations.GetRange(i, Math.Min(nSize, locations.Count - i)); 
    }  
} 

根据Dimitry Pavlov的回答,我将删除. tolist()。还要避免使用匿名类。 相反,我喜欢使用不需要分配堆内存的结构体。(ValueTuple也可以做这个工作。)

public static IEnumerable<IEnumerable<TSource>> ChunkBy<TSource>(this IEnumerable<TSource> source, int chunkSize)
{
    if (source is null)
    {
        throw new ArgumentNullException(nameof(source));
    }
    if (chunkSize <= 0)
    {
        throw new ArgumentOutOfRangeException(nameof(chunkSize), chunkSize, "The argument must be greater than zero.");
    }

    return source
        .Select((x, i) => new ChunkedValue<TSource>(x, i / chunkSize))
        .GroupBy(cv => cv.ChunkIndex)
        .Select(g => g.Select(cv => cv.Value));
} 

[StructLayout(LayoutKind.Auto)]
[DebuggerDisplay("{" + nameof(ChunkedValue<T>.ChunkIndex) + "}: {" + nameof(ChunkedValue<T>.Value) + "}")]
private struct ChunkedValue<T>
{
    public ChunkedValue(T value, int chunkIndex)
    {
        this.ChunkIndex = chunkIndex;
        this.Value = value;
    }

    public int ChunkIndex { get; }

    public T Value { get; }
}

这可以像下面这样使用,只在集合上迭代一次 也不分配任何重要内存。

int chunkSize = 30;
foreach (var chunk in collection.ChunkBy(chunkSize))
{
    foreach (var item in chunk)
    {
        // your code for item here.
    }
}

如果确实需要一个具体的列表,我会这样做:

int chunkSize = 30;
var chunkList = new List<List<T>>();
foreach (var chunk in collection.ChunkBy(chunkSize))
{
    // create a list with the correct capacity to be able to contain one chunk
    // to avoid the resizing (additional memory allocation and memory copy) within the List<T>.
    var list = new List<T>(chunkSize);
    list.AddRange(chunk);
    chunkList.Add(list);
}
List<int> orginalList =new List<int>(){1,2,3,4,5,6,7,8,9,10,12};
Dictionary<int,List<int>> dic = new Dictionary <int,List<int>> ();
int batchcount = orginalList.Count/2; //To List into two 2 parts if you 
 want three give three
List<int> lst = new List<int>();
for (int i=0;i<orginalList.Count; i++)
{
lst.Add(orginalList[i]);
if (i % batchCount == 0 && i!=0)
{
Dic.Add(threadId, lst);
lst = new List<int>();**strong text**
threadId++;
}
}
if(lst.Count>0)
Dic.Add(threadId, lst); //in case if any dayleft 
foreach(int BatchId in Dic.Keys)
{
  Console.Writeline("BatchId:"+BatchId);
  Console.Writeline('Batch Count:"+Dic[BatchId].Count);
}

你可以只使用LINQ简单地尝试以下代码:

public static IList<IList<T>> Split<T>(IList<T> source)
{
    return  source
        .Select((x, i) => new { Index = i, Value = x })
        .GroupBy(x => x.Index / 3)
        .Select(x => x.Select(v => v.Value).ToList())
        .ToList();
}