How to split an array into chunks of specific size? [closed]

Array.Copy has been around since 1.1 and does an excellent job of chunking arrays.

string[] buffer;for(int i = 0; i < source.Length; i+=100){    buffer = new string[100];    Array.Copy(source, i, buffer, 0, 100);    // process array}

And to make an extension for it:

public static class Extensions{    public static T[] Slice<T>(this T[] source, int index, int length)    {               T[] slice = new T[length];        Array.Copy(source, index, slice, 0, length);        return slice;    }}

And to use the extension:

string[] source = new string[] { 1200 items here };// get the first 100string[] slice = source.Slice(0, 100);

Update: I think you might be wanting ArraySegment<> No need for performance checks, because it simply uses the original array as its source and maintains an Offset and Count property to determine the 'segment'. Unfortunately, there isn't a way to retrieve JUST the segment as an array, so some folks have written wrappers for it, like here: ArraySegment - Returning the actual segment C#

ArraySegment<string> segment;for (int i = 0; i < source.Length; i += 100){    segment = new ArraySegment<string>(source, i, 100);    // and to loop through the segment    for (int s = segment.Offset; s < segment.Array.Length; s++)    {        Console.WriteLine(segment.Array[s]);    }}

Performance of Array.Copy vs Skip/Take vs LINQ

Test method (in Release mode):

static void Main(string[] args){    string[] source = new string[1000000];    for (int i = 0; i < source.Length; i++)    {        source[i] = "string " + i.ToString();    }    string[] buffer;    Console.WriteLine("Starting stop watch");    Stopwatch sw = new Stopwatch();    for (int n = 0; n < 5; n++)    {        sw.Reset();        sw.Start();        for (int i = 0; i < source.Length; i += 100)        {            buffer = new string[100];            Array.Copy(source, i, buffer, 0, 100);        }        sw.Stop();        Console.WriteLine("Array.Copy: " + sw.ElapsedMilliseconds.ToString());        sw.Reset();        sw.Start();        for (int i = 0; i < source.Length; i += 100)        {            buffer = new string[100];            buffer = source.Skip(i).Take(100).ToArray();        }        sw.Stop();        Console.WriteLine("Skip/Take: " + sw.ElapsedMilliseconds.ToString());        sw.Reset();        sw.Start();        String[][] chunks = source                                        .Select((s, i) => new { Value = s, Index = i })                                        .GroupBy(x => x.Index / 100)                                        .Select(grp => grp.Select(x => x.Value).ToArray())                                        .ToArray();        sw.Stop();        Console.WriteLine("LINQ: " + sw.ElapsedMilliseconds.ToString());    }    Console.ReadLine();}

Results (in milliseconds):

Array.Copy:    15Skip/Take:  42464LINQ:         881Array.Copy:    21Skip/Take:  42284LINQ:         585Array.Copy:    11Skip/Take:  43223LINQ:         760Array.Copy:     9Skip/Take:  42842LINQ:         525Array.Copy:    24Skip/Take:  43134LINQ:         638

You can use LINQ to group all items by the chunk size and create new Arrays afterwards.

// build sample data with 1200 Stringsstring[] items = Enumerable.Range(1, 1200).Select(i => "Item" + i).ToArray();// split on groups with each 100 itemsString[][] chunks = items                    .Select((s, i) => new { Value = s, Index = i })                    .GroupBy(x => x.Index / 100)                    .Select(grp => grp.Select(x => x.Value).ToArray())                    .ToArray();for (int i = 0; i < chunks.Length; i++){    foreach (var item in chunks[i])        Console.WriteLine("chunk:{0} {1}", i, item);}

Note that it's not necessary to create new arrays(needs cpu cycles and memory). You could also use the IEnumerable<IEnumerable<String>> when you omit the two ToArrays.

Here's the running code: http://ideone.com/K7Hn2

here I found another linq-solution:

int[] source = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };int i = 0;int chunkSize = 3;int[][] result = source.GroupBy(s => i++ / chunkSize).Select(g => g.ToArray()).ToArray();//result = [1,2,3][4,5,6][7,8,9]