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86d333ee94
* chore: Switch to Node 20 + Vitest * chore: migrate to vitest mock functions * chore: code style (switch to prettier) * test: re-enable long-running test Seems the switch to Node 20 and Vitest has vastly improved the code's and / or the test's runtime! see #1193 * chore: code style * chore: fix failing tests * Updated Documentation in README.md * Update contribution guidelines to state usage of Prettier * fix: set prettier printWidth back to 80 * chore: apply updated code style automatically * fix: set prettier line endings to lf again * chore: apply updated code style automatically --------- Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com> Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
104 lines
2.3 KiB
JavaScript
104 lines
2.3 KiB
JavaScript
/**
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* Author: Arnab Ray
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* ConvexHull using Graham Scan
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* Wikipedia: https://en.wikipedia.org/wiki/Graham_scan
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* Given a set of points in the plane. The Convex hull of the set is the smallest
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* convex polygon that contains all the points of it.
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*/
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function compare(a, b) {
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// Compare Function to Sort the points, a and b are points to compare
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if (a.x < b.x) return -1
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if (a.x === b.x && a.y < b.y) return -1
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return 1
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}
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function orientation(a, b, c) {
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// Check orientation of Line(a,b) and Line(b,c)
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const alpha = (b.y - a.y) / (b.x - a.x)
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const beta = (c.y - b.y) / (c.x - b.x)
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// Clockwise
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if (alpha > beta) return 1
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// Anticlockwise
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else if (beta > alpha) return -1
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// Colinear
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return 0
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}
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function convexHull(points) {
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const pointsLen = points.length
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if (pointsLen <= 2) {
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throw new Error('Minimum of 3 points is required to form closed polygon!')
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}
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points.sort(compare)
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const p1 = points[0]
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const p2 = points[pointsLen - 1]
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// Divide Hull in two halves
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const upperPoints = []
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const lowerPoints = []
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upperPoints.push(p1)
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lowerPoints.push(p1)
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for (let i = 1; i < pointsLen; i++) {
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if (i === pointsLen - 1 || orientation(p1, points[i], p2) !== -1) {
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let upLen = upperPoints.length
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while (
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upLen >= 2 &&
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orientation(
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upperPoints[upLen - 2],
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upperPoints[upLen - 1],
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points[i]
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) === -1
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) {
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upperPoints.pop()
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upLen = upperPoints.length
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}
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upperPoints.push(points[i])
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}
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if (i === pointsLen - 1 || orientation(p1, points[i], p2) !== 1) {
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let lowLen = lowerPoints.length
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while (
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lowLen >= 2 &&
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orientation(
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lowerPoints[lowLen - 2],
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lowerPoints[lowLen - 1],
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points[i]
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) === 1
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) {
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lowerPoints.pop()
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lowLen = lowerPoints.length
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}
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lowerPoints.push(points[i])
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}
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}
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const hull = []
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for (let i = 1; i < upperPoints.length - 1; i++) {
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hull.push(upperPoints[i])
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}
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for (let i = lowerPoints.length - 1; i >= 0; i--) {
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hull.push(lowerPoints[i])
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}
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return hull
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}
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export { convexHull }
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// Example
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// const points = [
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// { x: 0, y: 3 },
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// { x: 1, y: 1 },
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// { x: 2, y: 2 },
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// { x: 4, y: 4 },
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// { x: 0, y: 0 },
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// { x: 1, y: 2 },
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// { x: 3, y: 1 },
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// { x: 3, y: 3 }]
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// convexHull(points)
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