I am trying to get a list of numbers (upto 9) that don't contain any numbers already in a 3x3 cell from which is contained within a 81 large 2d array of integers. I'm attempting to make sudoku. There are likely better solutions that have nothing to with skipwhile or something similar, but they all seem to rely on duplicate numbers having the same index in both array which doesn't work.

int[] inCellNumbers = thisCell.Intersect(Numbers).ToArray();
int[] availableNumbers = Numbers.SkipWhile(Numbers.Contains<int>(inCellNumbers) == true);

This is the code that I tried, numbers is an array of integers and I get this error:

'MemoryExtensions.Contains(ReadOnlySpan, int)' requires a receiver of type 'ReadOnlySpan'

I was attempting to skip all numbers that are in 'inCellNumbers' and have them in 'availableNumbers' from 'Numbers'

CodePudding user response：

You can use the Enumerable.Except Method:

int[] availableNumbers = Numbers.Except(inCellNumbers).ToArray();

The Enumerable.SkipWhile Method stops skipping at the first element that does not fulfill the condition. Even if others follow later that do fulfill it.

CodePudding user response：

I'm not sure of the algorithm for checking around a sudoku grid but it sounds like you would want to use some hashsets.

A hashset may only have unique entries. An array or list can be dumped to a hashset using its constructor new HashSet(arrOrList), and you can evaluate immediately to one from LINQ using .ToHashSet().

As for the error, it looks like you are using List<T>.Contains<T>(T item) (notice all of the T here), which is going to check if the List contains the entire parameterized array as a single element/item. Unless Numbers is of type List<int[]> this is going to be a problem, but I'm unsure of what type you give it so this may not be the true issue. I see you are using .Contains<int> but this won't work as inCellNumbers is int[]