Add Graham scan in Rust #479
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| sort_based_on_lowest_coordinate(&mut points); | ||
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| // Take ownership of the pivot point | ||
| let pivot: Point = points.remove(0); |
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You usually don't state the types explicitly in Rust, especially when they're clear from the context (which in this case they are)
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Don't forget to add code imports to the .md file. |
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@ThijsRay If you do a rebase on top of current master, I'll review this. |
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| Point { x: 0.0, y: 2.0 }, | ||
| Point { x: 2.0, y: 2.0 }, | ||
| Point { x: 3.0, y: 4.0 }, | ||
| Point { x: 3.0, y: 1.0 }, |
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Can you change these points to be the ones from the Julia example?
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| // Calculate the polar angle of a point relative to a reference point. | ||
| fn polar_angle(reference: &Point, point: &Point) -> f64 { | ||
| (point.y - point.y).atan2(point.x - reference.x) |
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| (point.y - point.y).atan2(point.x - reference.x) | |
| (point.y - reference.y).atan2(point.x - reference.x) |
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| // Sort all points based on the angle between the pivot point and itself | ||
| &mut points | ||
| .sort_by(|a, b| (polar_angle(a, &pivot).partial_cmp(&polar_angle(b, &pivot))).unwrap()); |
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| .sort_by(|a, b| (polar_angle(a, &pivot).partial_cmp(&polar_angle(b, &pivot))).unwrap()); | |
| .sort_by(|a, b| (polar_angle(&pivot, a).partial_cmp(&polar_angle(&pivot, b))).unwrap()); |
for consistency with the polar_angle arguments.
| while counter_clockwise(&points[m - 1], &points[m], &points[i]) { | ||
| if m > 1 { | ||
| m -= 1; | ||
| } else if m == i { |
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| } else if m == i { | |
| } else if i == n { |
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| // Check if the turn of the points is counter clockwise. | ||
| fn counter_clockwise(a: &Point, b: &Point, c: &Point) -> bool { | ||
| (b.x - a.x) * (c.y - a.y) >= (b.y - a.y) * (c.x - a.x) |
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| (b.x - a.x) * (c.y - a.y) >= (b.y - a.y) * (c.x - a.x) | |
| (b.x - a.x) * (c.y - a.y) <= (b.y - a.y) * (c.x - a.x) |
if you want this function to return a bool.
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I missed something in my previous review, which is that in order to be consistent with the text (https://www.algorithm-archive.org/contents/graham_scan/graham_scan.html),
If the output of this function is 0, the points are collinear. If the output is positive, then the points form a counter-clockwise "left" turn. If the output is negative, then the points form a clockwise "right" turn. We basically do not want clockwise rotations, because this means we are at an interior angle.
this should return an integer.
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| // Check if the turn of the points is counter clockwise. | ||
| fn counter_clockwise(a: &Point, b: &Point, c: &Point) -> bool { | ||
| (b.x - a.x) * (c.y - a.y) >= (b.y - a.y) * (c.x - a.x) |
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I missed something in my previous review, which is that in order to be consistent with the text (https://www.algorithm-archive.org/contents/graham_scan/graham_scan.html),
If the output of this function is 0, the points are collinear. If the output is positive, then the points form a counter-clockwise "left" turn. If the output is negative, then the points form a clockwise "right" turn. We basically do not want clockwise rotations, because this means we are at an interior angle.
this should return an integer.
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@ThijsRay poke. |
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@ThijsRay I'm going to branch off this one and finish it off. I'll credit you of course. If you want to finish it yourself let me know and I'll leave you to it |
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Closing in favor of #964 based on this branch, thank you for your work! |
* Implement Graham Scan in Rust * Add Thijs * Remove compiled binary * Define ordering of points for sorting * Clean up code * Change points to match other implementations * Apply requested changes from #479 * Fix function signature * Add function comment * Change algorithm to simpler version from python * Fix points to match other languages * Adjust line numbers for rust * Apply clippy suggestions Co-authored-by: Thijs Raymakers <[email protected]> Co-authored-by: Sammy Plat <[email protected]> Co-authored-by: Dimitri Belopopsky <[email protected]>
This pull request aims to implement Graham Scan in Rust.