Need help with a slope-trick problem

Revision en1, by nhphuc, 2025-09-03 17:41:02

Link to problem.

Summary: Given $$$n$$$ segments, $$$i$$$-th segment is $$$(l_i,\ r_i)$$$. In one operation you can choose any $$$i$$$-th segment and increment or decrement both $$$l_i$$$ and $$$r_i$$$ by $$$1$$$. Find the minimum number of operations required to make each segment $$$i$$$ $$$(1 \lt i\leq n)$$$ intersect with segment $$$i - 1$$$.

I know how the dynamic programming works for this problem, and that it needs a slope-trick optimization, but I don't know how the two ideas work together (I have an AC submission but I don't actually understand how it works or the idea behind it). Please help me. Thanks for your attention — have a good day!

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en1 English nhphuc 2025-09-03 17:41:02 711 Initial revision (published)