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Given an n x n grid with some lamps that illuminate their entire row, column, and both diagonals, answer a sequence of queries asking whether a cell is illuminated and then turn off any lamp in the 3x3 neighborhood around that query. The challenge is to support up to 2e4 lamps/queries on a grid as large as 1e9 by efficiently tracking active lamps and aggregate illumination of rows, columns, and diagonals.
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Leetcode 1001. Grid Illumination
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Source snapshot: Nov 12, 2026
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