C#C
C#•3y ago
starshinata

Can't understand why this solution for a HackerRank problem is not working

Here is the link to the problem: https://www.hackerrank.com/challenges/count-triplets-1/problem?isFullScreen=true&h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=dictionaries-hashmaps

Here is my solution: (fails for test cases 6 and 10)
private static long GetNumberOfTriplets(long[] array, long ratio)
{
    var frequencyByInteger = array
        .GroupBy(item => item)
        .ToDictionary(g => g.Key, g => g.LongCount());

    if (ratio == 1) return frequencyByInteger.Values.Sum(v => v * (v - 1) * (v - 2) / 6);

    return array.Distinct()
        .Where(v => frequencyByInteger.ContainsKey(v * ratio)
                    && frequencyByInteger.ContainsKey(v * ratio * ratio))
        .Sum(v => frequencyByInteger[v] * frequencyByInteger[v * ratio] * frequencyByInteger[v * ratio * ratio]);
}


I know there are a lot of solutions to this online, but I want to specifically understand why the above solution is not correct. My current assumption is that I've found something nobody else before me has found and it's a HackerRank bug, meaning my code is correct. Would be happy to be proven wrong.
HackerRank
Count Triplets | HackerRank
Return the count of triplets that form a geometric progression.
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