C#-空数组上的笛卡尔

我需要6个数组的笛卡尔积-不足之处是在任何时候最多5个数组都可以为空.当所有数组都已填充时,它的效果很好,但是当任何一个数组为null时,它就会炸弹

我的数组是这样的

MatrixArray_1[0] = 1
MatrixArray_1[1] = 2

MatrixArray_2[0] = null
MatrixArray_2[1] = null

MatrixArray_n[0] = 2
MatrixArray_n[1] = 2

等等

我目前正在使用此代码…来自
http://blogs.msdn.com/b/ericlippert/archive/2010/06/28/computing-a-cartesian-product-with-linq.aspx

var product1 =  from first in MatrixArray_1
                from second in MatrixArray_2
                from third in MatrixArray_3
                from fourth in MatrixArray_4
                from fifth in MatrixArray_5
                from sixth in MatrixArray_6
                select new[] { first, second, third, fourth, fifth, sixth };
            string[][] myCombos_linq = product1.ToArray();

我试过将MatrixArray_n放在第一个！= null处,但会在第一个null数组处停止,并且不会读取所有剩余的数组,因此即使填充了array1和array 3,我的返回数组也始终为0行.

更改代码/逻辑的任何东西,在这一点上,不胜感激！
TIA

解决方法:

由于Eric的方法是使用IEnumerable< IEnumerable< T>&gt ;,因此您必须执行以下操作：

埃里克(Eric)的代码：

static IEnumerable<IEnumerable<T>> CartesianProduct<T>(this IEnumerable<IEnumerable<T>> sequences) 
{ 
  IEnumerable<IEnumerable<T>> emptyProduct = new[] { Enumerable.Empty<T>() }; 
  return sequences.Aggregate( 
    emptyProduct, 
    (accumulator, sequence) => 
      from accseq in accumulator 
      from item in sequence 
      select accseq.Concat(new[] {item})); 
}

致电地点：

var sequences = new int?[][] { MatrixArray_1, MatrixArray_2, ..., MatrixArray_6 };
var cartesianSequence = sequences.CartesianProduct();

更改通话地点：

var cartesianSequence = sequences.Where(a => a.Any(e => e != null)).CartesianProduct();

Where调用将排除所有元素均为空的序列.

要排除空数组以及仅包含空值的数组：

var cartesianSequence = sequences.Where(a => a != null && a.Any(e => e != null)).CartesianProduct();

或者,通过查询理解：

var filteredSequences = 
    from sequence in sequences
    where sequence != null && sequence.Any(e => e != null)
    select sequence
var cartesianSequence = filteredSequences.CartesianProduct();

编辑

另一种可能性是,即使某些元素非空,您也希望排除每个序列的空元素：

var filteredSequences = 
    from sequence in sequences
    where sequence != null && sequence.Any(e => e != null)
    select (from v in sequence where v.HasValue select s)
var cartesianSequence = filteredSequences.CartesianProduct();

要么

var cartesianSequence = sequences
    .Where(s => s != null && s.Any(e => e != null))
    .Select(s => s.Where(v => v != null))
    .CartesianProduct();

但是,由于我们不知道您在对结果做些什么,因此很难确切知道该如何建议.

标签：cartesian,linq,arrays,c
来源： https://codeday.me/bug/20191101/1985501.html