📜 WAYPOINT LESSON
Checkpoint — The Shifting Total
⭐⭐⭐ advanced⏳ 30 min read📍 Lesson 273 of 281
Range add, range sum: brute banks subtask 1, a double BIT unlocks the rest, and the O(Q^2) overlap list TLEs exactly like it would in a real contest.
Điểm kiểm tra — Tổng đang trôi. The classic lazy-propagation shape in its cheapest dress: range add, range sum. Bank the brute subtask, then the double BIT. The wrong solution is the honest villain: it is correct — just O(Q²) — and dies exactly the way a correct-but-slow submission dies in a real contest: on the clock, not on the logic.