initial implementation sweeplineff
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@@ -1,5 +1,7 @@
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using System.Collections;
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using Medallion.Collections;
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namespace TMI_practicum
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{
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@@ -7,7 +9,193 @@ namespace TMI_practicum
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{
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public static IEnumerable<Intersection> Solve(IEnumerable<Circle> circles)
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{
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return null;
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var intersections = new Stack<Intersection>();
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var events = new PriorityQueue<Event>();
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var upperActive = new CircleTree<SegmentKey, Segment>();
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var bottomActive = new CircleTree<SegmentKey, Segment>();
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foreach (var circle in circles)
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{
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events.Enqueue(new Event(Event.EventType.Start, circle.X - circle.R, circle));
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events.Enqueue(new Event(Event.EventType.End, circle.X + circle.R, circle));
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}
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while (events.Count != 0)
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{
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Event e = events.Dequeue();
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int hash = e.GetHashCode();
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switch (e.Type)
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{
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case Event.EventType.Start:
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upperActive.Add(new SegmentKey(e.X, e.Circle.Y, Segment.SegmentType.Upper, hash),
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new Segment(Segment.SegmentType.Upper, e.Circle.Y, e.Circle));
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bottomActive.Add(new SegmentKey(e.X, e.Circle.Y, Segment.SegmentType.Bottom, hash),
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new Segment(Segment.SegmentType.Bottom, e.Circle.Y, e.Circle));
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CheckIntersections(upperActive, e, intersections, true);
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CheckIntersections(bottomActive, e, intersections, false);
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break;
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case Event.EventType.End:
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upperActive.Remove(new SegmentKey(e.X, e.Circle.Y, Segment.SegmentType.Upper, hash));
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bottomActive.Remove(new SegmentKey(e.X, e.Circle.Y, Segment.SegmentType.Bottom, hash));
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break;
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default:
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throw new ArgumentOutOfRangeException();
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}
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}
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return intersections;
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}
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private static void CheckIntersections(CircleTree<SegmentKey, Segment> active, Event e, Stack<Intersection> intersections, bool upper)
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{
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Segment other;
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try
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{
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other = upper
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? active.FindSuccessor(new SegmentKey(e.X, e.Circle.Y, Segment.SegmentType.Upper, e.GetHashCode()))
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: active.FindPredecessor(new SegmentKey(e.X, e.Circle.Y, Segment.SegmentType.Bottom, e.GetHashCode()));
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}
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catch (KeyNotFoundException)
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{
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return;
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}
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var intersects = e.Circle.FindIntersections(other.Circle);
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if (intersects == null) return;
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foreach (var intersection in intersects)
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{
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if (upper)
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{
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if (intersection.Y < e.Circle.Y) continue;
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}
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else
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{
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if (intersection.Y > e.Circle.Y) continue;
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}
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intersections.Push(intersection);
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}
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}
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private class CircleTree<TKey, TValue> : SortedDictionary<TKey, TValue>
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{
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public TValue FindSuccessor(TKey key)
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{
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var other = this.Keys.Where(s => this.Comparer.Compare(s, key) > 0).MinOrDefault();
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return this[other];
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}
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public TValue FindPredecessor(TKey key)
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{
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var other = this.Keys.Where(s => this.Comparer.Compare(s, key) < 0).MaxOrDefault();
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return this[other];
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}
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}
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private struct Event : IComparable<Event>
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{
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public EventType Type { get; }
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public Circle Circle { get; }
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public double X { get; }
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public enum EventType
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{
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Start,
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Intersect,
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End
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}
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public Event(EventType type, double x, Circle circle)
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{
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Type = type;
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X = x;
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Circle = circle;
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}
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public int CompareTo(Event other)
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{
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return X.CompareTo(other.X);
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}
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}
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private class Segment : IComparable<Segment>
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{
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public Segment(SegmentType type, double y, Circle circle)
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{
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_type = type;
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_y = y;
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Circle = circle;
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}
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private readonly SegmentType _type;
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private readonly double _y;
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public Circle Circle { get; }
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public int CompareTo(Segment other)
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{
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throw new NotImplementedException();
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}
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public enum SegmentType
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{
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Bottom,
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Upper,
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Null
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}
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}
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private struct SegmentKey : IComparable<SegmentKey>
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{
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private readonly double _x;
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private readonly double _y;
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private readonly Segment.SegmentType _type;
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private readonly int _identifier;
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public SegmentKey(double x, double y, Segment.SegmentType type, int identifier)
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{
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_y = y;
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_type = type;
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_identifier = identifier;
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_x = x;
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}
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public int CompareTo(SegmentKey other)
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{
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if (_identifier.Equals(other._identifier)) return _type.CompareTo(other._type);
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if (!_y.Equals(other._y)) return _y.CompareTo(other._y);
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return _type.Equals(other._type) ? _x.CompareTo(other._x) : _type.CompareTo(other._type);
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}
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public override bool Equals(object obj)
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{
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if (obj == null || GetType() != obj.GetType()) return false;
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SegmentKey r = (SegmentKey) obj;
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return _identifier.Equals(r._identifier) && _type.Equals(r._type);
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}
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public override int GetHashCode()
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{
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return _identifier.GetHashCode() ^ _type.GetHashCode();
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}
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}
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}
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public static class EnumerableExtensions
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{
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public static T MinOrDefault<T>(this IEnumerable<T> sequence)
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{
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return sequence.Any() ? sequence.Min() : default(T);
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}
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public static T MaxOrDefault<T>(this IEnumerable<T> sequence)
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{
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return sequence.Any() ? sequence.Max() : default(T);
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}
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}
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}
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