Interval Sign Flips

Given an integer array and a list of intervals, flip the sign of every element inside each interval, then return the final array. Requirements Input: an integer array arr and a list of intervals. For each interval, negate every number in the covered range: +1 -> -1, -5 -> 5, and so on. Apply intervals in order, then return the final array. Clarify whether interval endpoints are inclusive and whether indices are 0-based or 1-based before coding. Notes Direct simulation is fine if constraints are small. If the array and interval list are large, use a difference array over parity: each covered index only needs to know whether it was flipped an odd or even number of times. Inclusive endpoints are the likely off-by-one trap. In a difference-array solution, an inclusive interval [l, r] toggles at l and at r + 1. A value of 0 remains 0 after sign flips. Preparation Implement the direct simulation first, then rewrite it with a parity difference array. Test overlapping intervals, repeated identical intervals, a single-element interval, and an interval covering the whole array.