Data commit

Task/Convex-hull/C-sharp/convex-hull.cs

@@ -0,0 +1,96 @@
+using System;
+using System.Collections.Generic;
+
+namespace ConvexHull {
+    class Point : IComparable<Point> {
+        private int x, y;
+
+        public Point(int x, int y) {
+            this.x = x;
+            this.y = y;
+        }
+
+        public int X { get => x; set => x = value; }
+        public int Y { get => y; set => y = value; }
+
+        public int CompareTo(Point other) {
+            return x.CompareTo(other.x);
+        }
+
+        public override string ToString() {
+            return string.Format("({0}, {1})", x, y);
+        }
+    }
+
+    class Program {
+        private static List<Point> ConvexHull(List<Point> p) {
+            if (p.Count == 0) return new List<Point>();
+            p.Sort();
+            List<Point> h = new List<Point>();
+
+            // lower hull
+            foreach (var pt in p) {
+                while (h.Count >= 2 && !Ccw(h[h.Count - 2], h[h.Count - 1], pt)) {
+                    h.RemoveAt(h.Count - 1);
+                }
+                h.Add(pt);
+            }
+
+            // upper hull
+            int t = h.Count + 1;
+            for (int i = p.Count - 1; i >= 0; i--) {
+                Point pt = p[i];
+                while (h.Count >= t && !Ccw(h[h.Count - 2], h[h.Count - 1], pt)) {
+                    h.RemoveAt(h.Count - 1);
+                }
+                h.Add(pt);
+            }
+
+            h.RemoveAt(h.Count - 1);
+            return h;
+        }
+
+        private static bool Ccw(Point a, Point b, Point c) {
+            return ((b.X - a.X) * (c.Y - a.Y)) > ((b.Y - a.Y) * (c.X - a.X));
+        }
+
+        static void Main(string[] args) {
+            List<Point> points = new List<Point>() {
+                new Point(16, 3),
+                new Point(12, 17),
+                new Point(0, 6),
+                new Point(-4, -6),
+                new Point(16, 6),
+
+                new Point(16, -7),
+                new Point(16, -3),
+                new Point(17, -4),
+                new Point(5, 19),
+                new Point(19, -8),
+
+                new Point(3, 16),
+                new Point(12, 13),
+                new Point(3, -4),
+                new Point(17, 5),
+                new Point(-3, 15),
+
+                new Point(-3, -9),
+                new Point(0, 11),
+                new Point(-9, -3),
+                new Point(-4, -2),
+                new Point(12, 10)
+            };
+
+            List<Point> hull = ConvexHull(points);
+            Console.Write("Convex Hull: [");
+            for (int i = 0; i < hull.Count; i++) {
+                if (i > 0) {
+                    Console.Write(", ");
+                }
+                Point pt = hull[i];
+                Console.Write(pt);
+            }
+            Console.WriteLine("]");
+        }
+    }
+}