Implement Graham Scan in Rust

Author: ThijsRay

contents/graham_scan/code/rust/graham_scan.rs

@@ -0,0 +1,74 @@
+#[derive(Debug)]
+struct Point {
+    x: f64,
+    y: f64,
+}
+
+// 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))
+}
+
+// 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)
+}
+
+fn graham_scan(mut points: Vec<Point>) -> Vec<Point> {
+    // First, sort the points so the one with the lowest y-coordinate comes first (the pivot)
+    sort_based_on_lowest_coordinate(&mut points);
+
+    // Take ownership of the pivot point
+    let pivot: Point = points.remove(0);
+
+    // 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());
+
+    // Reinsert the pivot point
+    points.insert(0, pivot);
+
+    let n = points.len();
+    let mut m = 1;
+
+    // Move the points of the hull towards the beginning of the vector.
+    for mut i in 2..n {
+        while counter_clockwise(&points[m - 1], &points[m], &points[i]) {
+            if m > 1 {
+                m -= 1;
+            } else if m == i {
+                break;
+            } else {
+                i += 1;
+            }
+        }
+
+        m += 1;
+        points.swap(i, m);
+    }
+
+    // Remove all non-hull points from the vector
+    points.truncate(m + 2);
+    points
+}
+
+fn sort_based_on_lowest_coordinate(points: &mut Vec<Point>) {
+    points.sort_unstable_by(|a, b| (a.x).partial_cmp(&b.x).unwrap());
+    points.sort_by(|a, b| (a.y).partial_cmp(&b.y).unwrap());
+}
+
+fn main() {
+    let points = vec![
+        Point { x: 1.0, y: 3.0 },
+        Point { x: 2.0, y: 4.0 },
+        Point { x: 4.0, y: 0.0 },
+        Point { x: 1.0, y: 0.0 },
+        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 },
+    ];
+
+    let hull_points = graham_scan(points);
+    println!("{:#?}", hull_points);
+}