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A sweep-line algorithm processes geometric events in the order a conceptual line crosses a plane. It keeps an event queue and a status describing objects intersecting the current line. For horizontal and vertical line segments, sweep left to right: insert a horizontal segment at its left endpoint, query active heights at a vertical segment, and delete horizontals at their right endpoints. A balanced search structure supports the updates and range reporting. Equal-coordinate event ordering determines whether endpoint contacts count. The method reduces a two-dimensional problem to a changing one-dimensional ordering rather than physically sampling every line position.