Get Triple Count

Problem Overview

• Count distinct triplets (i<j<k) in an array whose sum is divisible by d.
• Input: arr of stock prices and integer d; Output: integer count; constraints: 3<=n<=10^3, 1<=arr[i]<=10^9, 2<=d<=10^6.
• Real-world context: selecting three days to buy stocks where their total cost meets a divisibility rule.
• From Ibm interviews; an interview question commonly used in a coding interview and posed as a screening problem.