We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
  1. Count Triplets
  2. Discussions

Count Triplets

  • Kanahaiya
     + 1 comment

    Hello friends,

    Today, I have explained the technique to solve Count Triplets hackerrank problem in O(N) time.

    click here for the video explanation of generic algorithm with complexity analysis.

    or you can click on the image too to follow youtube tutorial.

    Here is the 100% working solution:-

    source code :

    private static long countTriplets(List<Long> arr, long r) {
	Map<Long, Long> leftMap = new HashMap<>();
	Map<Long, Long> rightMap = new HashMap<>();

	for (long item : arr) {
		rightMap.put(item, rightMap.getOrDefault(item, 0L) + 1);
	}

	long count = 0;

	for (int i = 0; i < arr.size(); i++) {
		long midTerm = arr.get(i);
		long c1 = 0, c3 = 0;

		rightMap.put(midTerm, rightMap.getOrDefault(midTerm, 0L) - 1);

		if (leftMap.containsKey(midTerm / r) && midTerm % r == 0) {
			c1 = leftMap.get(midTerm / r);
		}

		if (rightMap.containsKey(midTerm * r))
			c3 = rightMap.get(midTerm * r);

		count += c1 * c3;

		leftMap.put(midTerm, leftMap.getOrDefault(midTerm, 0L) + 1);

	}
	return count;
}

    Would really appreciate your feedback like, dislike , comment etc. on my video.

    Do not forget to upvote, if you find it useful.