Question

I have a Dictionary containing 10 keys, each with a list containing up to 30,000 values. The values contain a DateTime property.

I frequently need to extract a small subset of one of the keys, like a date range of 30 – 60 seconds.

Doing this is easy, but getting it to run fast is not so. What would be the most efficient way to query this in-memory data?

Thanks a lot.

Answer 1

Sort lists by date at the first, then find your required items by binary search (i.e k item) and return them, finding the searched item is O(log(n)) because you need find first and last index. returning them is O(K) in all It’s O(K+log(n))

    IEnumerable<item> GetItems(int startIndex, int endIndex, List<item> input)
    {
        for (int i=startIndex;i<endIndex;i++)
           yield return input[i];
    }