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19 lines
777 B
JavaScript
19 lines
777 B
JavaScript
const findConvexHull = async (pts) => {
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const { sortBy, uniqBy } = await import('https://esm.sh/lodash-es@4');
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const cross = (a, b, c) => (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
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const sorted = sortBy(uniqBy(pts, p => `${p.x},${p.y}`), ['x', 'y']);
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if (sorted.length < 3) return sorted;
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const lower = [], upper = [];
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for (const p of sorted) {
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while (lower.length > 1 && cross(lower[lower.length-2], lower[lower.length-1], p) <= 0) lower.pop();
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lower.push(p);
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}
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for (let i = sorted.length - 1; i >= 0; i--) {
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const p = sorted[i];
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while (upper.length > 1 && cross(upper[upper.length-2], upper[upper.length-1], p) <= 0) upper.pop();
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upper.push(p);
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}
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lower.pop(); upper.pop();
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return [...lower, ...upper];
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};
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export default findConvexHull; |