如何按索引對項目進行分組？ C＃LINQ

Question

假設我有

var input = new int[] { 0, 1, 2, 3, 4, 5 }; 

如何讓他們分成對？

var output = new int[][] { new int[] { 0, 1 }, new int[] { 2, 3 }, new int[] { 4, 5 } }; 

最好使用LINQ

Answer 1

input 
    .Select((value, index) => new { PairNum = index/2, value }) 
    .GroupBy(pair => pair.PairNum) 
    .Select(grp => grp.Select(g => g.value).ToArray()) 
    .ToArray() 

Answer 2

var indexedNumbers = input.Select((number, index) => new { Index = index, Number = number }); 

var pairs = 
    from indexedNumber in indexedNumbers 
    group indexedNumber by indexedNumber.Index/2 into indexedNumberPair 
    select indexedNumberPair.Select(indexedNumber => indexedNumber.Number); 

var arrays = pairs.Select(pair => pair.ToArray()).ToArray(); 

Answer 3

可能並不適用於你，但你可以使用新的Zip方法在C＃4.0

var input = new int[] { 0, 1, 2, 3, 4, 5 }; 
IEnumerable evens = input.Where((element, index) => index % 2 == 0); 
IEnumerable odds = input.Where((element, index) => index % 2 == 1); 
var results = evens.Zip(odds, (e, o) => new[] { e, o }).ToArray(); 
 

Answer 4

var input = new int[] { 0, 1, 2, 3, 4, 5 }; 
int i = 0; 
var output = input.GroupBy(item => i++/2); 

Answer 5

使用ToLookup方法：

input 
    .Select((number, index) => new { index , number}) 
    .ToLookup(_ => _.index/2, _ => _.number) 
    .Select(_ => _.ToArray()) 
    .ToArray(); 

使用Zip方法：

input 
    .Zip(input.Skip(1), (_, __) => new[] {_, __}) 
    .Where((_, index) => index % 2 == 0) 
    .ToArray();