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  1. Count Triplets
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Count Triplets

  • babakhonza
     + 0 comments

    Eritorial transformed into Java. Don't forget to check if number is divisible by r.

        // Complete the countTriplets function below.
    static long countTriplets(List<Long> arr, long r) {
        HashMap<Long, Long> right = new HashMap<>();
        HashMap<Long, Long> left = new HashMap<>();
        
        for (Long num : arr) {
            right.put(num, right.getOrDefault(num, 0L) + 1);
        }
        
        long tripletsCounter = 0;
        
        for (Long num : arr) {
            if (right.getOrDefault(num, 0L) > 0) {
                right.put(num, right.get(num) - 1);
            }
            if (num % r == 0) {
                tripletsCounter += right.getOrDefault(num * r, 0L) * left.getOrDefault(num / r, 0L);
            }
            left.put(num, left.getOrDefault(num, 0L) + 1);
        }
        
        return tripletsCounter;
    }