Divide & Conquer Dynamic Programming Optimisation, CSES Subarray Squares

CSES Subarray Squares: https://cses.fi/problemset/task/2086 My code: https://cses.fi/paste/868eebff0bc4354... Convex Hull Trick tutorial:    • Convex Hull Trick - Dynamic Programming Op...   Quadrangle Inequality Insights: https://codeforces.com/blog/entry/86306 CP-Algorithms D&C DP tutorial: https://cp-algorithms.com/dynamic_pro... Practice problem: https://codeforces.com/contest/321/pr...