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Tidy up and optimise kd-tree

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This commit is contained in:
BobLd
2020-03-02 23:27:35 +00:00
committed by Eliot Jones
parent bef68a0654
commit e477bc8d6d
1 changed files with 27 additions and 28 deletions
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55
src/UglyToad.PdfPig.DocumentLayoutAnalysis/KdTree.cs
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@@ -24,53 +24,52 @@
public KdTree(IReadOnlyList<T> candidates, Func<T, PdfPoint> candidatesPointFunc)
{
var pointsIndex = Enumerable.Range(0, candidates.Count).Zip(candidates, (e, p) => (e, candidatesPointFunc(p), p)).ToList();
if (candidates != null && candidates.Count > 0)
if (candidates == null || candidates.Count == 0)
{
Root = BuildTree(pointsIndex, 0);
throw new ArgumentException("KdTree(): candidates cannot be null or empty.", nameof(candidates));
}
Root = BuildTree(
Enumerable.Range(0, candidates.Count).Zip(candidates, (e, p) => (e, candidatesPointFunc(p), p)).ToArray(),
candidates.Count, 0);
}
private KdTreeNode<T> BuildTree(IReadOnlyList<(int, PdfPoint, T)> P, int depth)
private KdTreeNode<T> BuildTree((int, PdfPoint, T)[] P, int length, int depth)
{
var median = P.Count / 2;
if (depth % 2 == 0) // depth is even
int median = length / 2;
if (depth % 2 == 0)
{
P = P.OrderBy(p => p.Item2.X).ToArray();
Array.Sort(P, (p0, p1) => p0.Item2.X.CompareTo(p1.Item2.X));
}
else
{
P = P.OrderBy(p => p.Item2.Y).ToArray();
Array.Sort(P, (p0, p1) => p0.Item2.Y.CompareTo(p1.Item2.Y));
}
// left side
var P1 = P.Take(median).ToArray();
KdTreeNode<T> vLeft = null;
if (P1.Length == 1)
if (median == 1)
{
var item = P1[0];
vLeft = new KdTreeLeaf<T>(item.Item2, item.Item3, depth, item.Item1);
vLeft = new KdTreeLeaf<T>(P[0], depth);
}
else if (P1.Length > 1)
else if (median > 1)
{
vLeft = BuildTree(P1, depth + 1);
vLeft = BuildTree(P.Take(median).ToArray(), median, depth + 1);
}
// right side
var P2 = P.Skip(median + 1).ToArray();
KdTreeNode<T> vRight = null;
if (P2.Length == 1)
if (median + 2 == length)
{
var item = P2[0];
vRight = new KdTreeLeaf<T>(item.Item2, item.Item3, depth, item.Item1);
vRight = new KdTreeLeaf<T>(P[median + 1], depth);
}
else if (P2.Length > 1)
else if (median + 2 < length)
{
vRight = BuildTree(P2, depth + 1);
vRight = BuildTree(P.Skip(median + 1).ToArray(), length - median - 1, depth + 1);
}
var medianItem = P[median];
return new KdTreeNode<T>(vLeft, vRight, medianItem.Item2, medianItem.Item3, depth, medianItem.Item1);
return new KdTreeNode<T>(vLeft, vRight, P[median], depth);
}
#region NN
@@ -155,8 +154,8 @@
{
public override bool IsLeaf => true;
public KdTreeLeaf(PdfPoint l, Q element, int depth, int index)
: base(null, null, l, element, depth, index)
public KdTreeLeaf((int, PdfPoint, Q) point, int depth)
: base(null, null, point, depth)
{ }
public override string ToString()
@@ -189,14 +188,14 @@
public int Index { get; }
public KdTreeNode(KdTreeNode<Q> leftChild, KdTreeNode<Q> rightChild, PdfPoint l, Q element, int depth, int index)
public KdTreeNode(KdTreeNode<Q> leftChild, KdTreeNode<Q> rightChild, (int, PdfPoint, Q) point, int depth)
{
LeftChild = leftChild;
RightChild = rightChild;
Value = l;
Element = element;
Value = point.Item2;
Element = point.Item3;
Depth = depth % 2;
Index = index;
Index = point.Item1;
}
public IEnumerable<KdTreeLeaf<Q>> GetLeaves()