city-generation/Game/Assets/Scripts/Utils/QuadTree.cs

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8.6 KiB
C#
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using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using TransportGame.Model;
namespace TransportGame.Utils
{
public class QuadTree<T>: ICollection<T> where T : IPositionable
{
private const int Capacity = 8;
/// <summary>
/// Gets the subtree in northwest position
/// </summary>
public QuadTree<T> NorthWest { get; private set; }
/// <summary>
/// Gets the subtree in northeast position
/// </summary>
public QuadTree<T> NorthEast { get; private set; }
/// <summary>
/// Gets the subtree in southeast position
/// </summary>
public QuadTree<T> SouthEast { get; private set; }
/// <summary>
/// Gets the subtree in southwest position
/// </summary>
public QuadTree<T> SouthWest { get; private set; }
/// <summary>
/// Gets the boundary of this quad tree
/// </summary>
public Rectangle Boundary { get; private set; }
private List<T> points = new List<T>(Capacity);
/// <summary>
/// Initializes a quad tree using specified boundaries
/// </summary>
/// <param name="left">Left</param>
/// <param name="top">Top</param>
/// <param name="right">Right</param>
/// <param name="bottom">Bottom</param>
public QuadTree(float left, float top, float right, float bottom)
{
Boundary = new Rectangle(left, top, right, bottom);
}
/// <summary>
/// Initializes a quad tree using specified boundaries
/// </summary>
/// <param name="boundary">Boundaries</param>
public QuadTree(Rectangle boundary)
{
Boundary = boundary;
}
private void Subdivide()
{
float midx = Boundary.Left + Boundary.Width / 2f;
float midy = Boundary.Top + Boundary.Height / 2f;
NorthWest = new QuadTree<T>(Boundary.Left, Boundary.Top, midx, midy);
NorthEast = new QuadTree<T>(midx, Boundary.Top, Boundary.Right, midy);
SouthEast = new QuadTree<T>(midx, midy, Boundary.Right, Boundary.Bottom);
SouthWest = new QuadTree<T>(Boundary.Left, midy, midx, Boundary.Bottom);
foreach (var point in points)
Add(point);
points.Clear();
}
private void Merge()
{
foreach (var point in NorthWest)
points.Add(point);
foreach (var point in NorthEast)
points.Add(point);
foreach (var point in SouthEast)
points.Add(point);
foreach (var point in SouthWest)
points.Add(point);
NorthWest = null;
NorthEast = null;
SouthEast = null;
SouthWest = null;
}
/// <summary>
/// Adds a point in this quad tree
/// </summary>
/// <param name="item">Point</param>
public void Add(T item)
{
// Precondition - point must be inside boundaries
if (!Boundary.Contains(item.Position))
throw new ArgumentException("Point must be inside boundaries.");
// Reached capacity, subdivide
if (NorthWest == null && points.Count >= Capacity)
Subdivide();
// Not divided in subtrees
if (NorthWest == null)
{
if (!points.Any(p => p.Position.Equals(item.Position)))
points.Add(item);
}
// Add in the right subtree
else
{
if (NorthWest.Boundary.Contains(item.Position))
NorthWest.Add(item);
else if (NorthEast.Boundary.Contains(item.Position))
NorthEast.Add(item);
else if (SouthEast.Boundary.Contains(item.Position))
SouthEast.Add(item);
else SouthWest.Add(item);
}
}
/// <summary>
/// Empties the entire tree
/// </summary>
public void Clear()
{
NorthWest = null;
NorthEast = null;
SouthEast = null;
SouthWest = null;
points.Clear();
}
/// <summary>
/// Tests if specified point is contained in this tree
/// </summary>
/// <param name="item">Point</param>
/// <returns>True if point is contained</returns>
public bool Contains(T item)
{
if (NorthWest == null)
return points.Contains(item);
else
return NorthWest.Contains(item) || NorthEast.Contains(item) || SouthEast.Contains(item) || SouthWest.Contains(item);
}
/// <summary>
/// Copies all points to specified array
/// </summary>
/// <param name="array">Array</param>
/// <param name="arrayIndex">Index where to start copying</param>
public void CopyTo(T[] array, int arrayIndex)
{
foreach (var point in this)
array[arrayIndex++] = point;
}
/// <summary>
/// Gets the number of points in this quad tree
/// </summary>
public int Count
{
get
{
return (NorthWest == null) ? points.Count : NorthWest.Count + NorthEast.Count + SouthEast.Count + SouthWest.Count;
}
}
/// <summary>
/// Returns true if this container is read-only.
/// </summary>
public bool IsReadOnly
{
get
{
return false;
}
}
/// <summary>
/// Removes an item from the tree
/// </summary>
/// <param name="item">Item to remove</param>
/// <returns>True if item was removed</returns>
public bool Remove(T item)
{
if (NorthWest == null)
return points.Remove(item);
else
{
bool result = NorthWest.Remove(item) || NorthEast.Remove(item) || SouthEast.Remove(item) || SouthWest.Remove(item);
// We can merge subdivisions
if (Count < (Capacity - Capacity / 3))
Merge();
return result;
}
}
/// <summary>
/// Gets an enumerator for this collection
/// </summary>
/// <returns></returns>
System.Collections.IEnumerator IEnumerable.GetEnumerator()
{
foreach (var point in this)
yield return point;
}
/// <summary>
/// Gets enumerator for this collection
/// </summary>
/// <returns></returns>
public IEnumerator<T> GetEnumerator()
{
if (NorthWest == null)
{
foreach (var point in points)
yield return point;
}
else
{
foreach (var point in NorthWest)
yield return point;
foreach (var point in NorthEast)
yield return point;
foreach (var point in SouthEast)
yield return point;
foreach (var point in SouthWest)
yield return point;
}
}
/// <summary>
/// Gets all the points in the specified region
/// </summary>
/// <param name="rect">Region</param>
/// <returns>Points</returns>
public IEnumerable<T> Query(Rectangle rect)
{
// No intersection
if (!Rectangle.Intersects(rect, Boundary))
return Enumerable.Empty<T>();
if (NorthWest == null)
{
return points.Where(p => rect.Contains(p.Position));
}
else
{
return NorthWest.Query(rect)
.Concat(NorthEast.Query(rect))
.Concat(SouthEast.Query(rect))
.Concat(SouthWest.Query(rect));
}
}
/// <summary>
/// Gets all the points in the specified region
/// </summary>
/// <param name="left">Left</param>
/// <param name="top">Top</param>
/// <param name="right">Right</param>
/// <param name="bottom">Bottom</param>
/// <returns>Points</returns>
public IEnumerable<T> Query(float left, float top, float right, float bottom)
{
return Query(new Rectangle(left, top, right, bottom));
}
}
}