Recently in a contest there was a DP problem which used a prefix-sum concept. I tried to implement it in bottom-up as well as in top-down. The bottom-up one got AC'ed but the top-down got a TLE on Test 3. I understand the reason for TLE but I am not able to implement that bottom-up prefix idea for this. Any ideas on how to solve the problem using top-down approach?

Problem link = http://codeforces.me/contest/1068/problem/D

Top-Down solution = https://pastebin.com/VYsA7cXj

Bottom-up solution = https://pastebin.com/5RryJeh5