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Check the grouping of values ​​in List <string>

In one of my programs, I need to check the grouping of items in a list. So I have values ​​in List<string>

. Here's an example of a list (in that order):

Women
's
Women
's Women 's Women 's
Women
's
Men
's
Men
's Men 's Men 's Women's

What I want to check is the grouping of this list. So the women downstairs shouldn't be there. This is the wrong grouping.

I CANNOT sort this list because there will be a special order for it, which is not simple as in the above list (and can have more than two different values) and always changes. However, grouping will be supported.

All I want to do is find the wrong grouping and display the error. I hope there is a better way to do this than to loop like crazy. Thank!

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3 answers


You should do this by traversing the elements and keeping track of the unique elements seen in HashSet<string>

and the previous value.



string previous = items.FirstOrDefault();
var seen = new HashSet<string>();
seen.Add(previous);

for (int i = 1; i < items.Count; i++)
{
    if (previous != items[i])
    {
        if (!seen.Add(items[i]))
        {
            Console.WriteLine("This item is not grouped:" + items[i] + " at index " + i);
        }

        previous = items[i];
    }
}
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foreach (string item in list.Distinct())
{
    int startIndex = list.IndexOf(item);
    int endIndex = list.LastIndexOf(item);

    bool notGrouped = Enumerable.Range(startIndex, endIndex - startIndex + 1).Select(index => list[index]).Any(i => i != item);
    if (notGrouped)
    {
        // show message for the current item
    }
}


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If I understand you correctly:

List<string> orgList = .......;
bool ok = orgList.GroupBy(x => x).SelectMany(x => x).SequenceEqual(orgList);
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