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34 lines
916 B
JavaScript
34 lines
916 B
JavaScript
async function findConvexHull(points) {
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const _ = await import('https://cdn.jsdelivr.net/npm/lodash@4.17.21/+esm');
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const uniqueSortedPoints = _.sortBy(
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_.uniqBy(points, p => `${p.x}:${p.y}`),
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['x', 'y']
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);
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if (uniqueSortedPoints.length < 3) {
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return uniqueSortedPoints;
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}
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const crossProduct = (p1, p2, p3) =>
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(p2.x - p1.x) * (p3.y - p1.y) - (p2.y - p1.y) * (p3.x - p1.x);
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const buildHalfHull = pts => {
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const half = [];
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for (const p of pts) {
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while (half.length >= 2 && crossProduct(half.at(-2), half.at(-1), p) <= 0) {
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half.pop();
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}
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half.push(p);
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}
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return half;
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};
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const lower = buildHalfHull(uniqueSortedPoints);
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const upper = buildHalfHull([...uniqueSortedPoints].reverse());
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const ccwHull = lower.slice(0, -1).concat(upper.slice(0, -1));
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return [ccwHull[0], ...ccwHull.slice(1).reverse()];
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}
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export default findConvexHull; |