I have a matrix, IEnumerable<IEnumerable<int>> matrix, for example:

{ {10,23,16,20,2,4},  {22,13,1,33,21,11 }, {7,19,31,12,6,22}, ... }

and another array:

int[] arr={ 10, 23, 16, 20}

I want to filter the matrix on the condition that I group all rows of the matrix which contain the same number of elements from arr.

That is to say the first row in the matrix {10,23,16,20,2,4} has 4 numbers from arr, this array should be grouped with the rest of the rows with 4 numbers from arr.

better to use linq, thank you very much!