Inside, Outside, or On the Fence — Solution & Editorial

Problems > Inside, Outside, or On the Fence > Editorial

Inside, Outside, or On the Fence — Solution & Editorial

Ray casting: count edge crossings of a horizontal ray; odd = inside. First test boundary membership exactly (collinear + within the edge's bounding box) using integer cross products.

Complexity: O(NQ)

Watch out: The border must be detected BEFORE the parity test, or on-edge points flip unpredictably.

Problems > Inside, Outside, or On the Fence > Editorial

Inside, Outside, or On the Fence — Solution & Editorial

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