Untitled

from collections import defaultdict

def get_triplet_count(arr, d):
    n = len(arr)
    count = 0

    # Dictionary to store frequency of (arr[i] + arr[j]) % d
    remainder_count = defaultdict(int)

    # Traverse each element as the third element in the triplet
    for k in range(n):
        # For every arr[k], find pairs (arr[i], arr[j]) that make the sum divisible by d
        target_remainder = (-arr[k]) % d
        if target_remainder in remainder_count:
            count += remainder_count[target_remainder]

        # Update remainder counts for pairs ending at k
        for j in range(k):
            pair_sum = (arr[j] + arr[k]) % d
            remainder_count[pair_sum] += 1

    return count

# Test case from the image
arr = [2, 3, 1, 6]
d = 3
result = get_triplet_count(arr, d)
result  # Expected output: 2