public int Compare(NodeMeasured <T> x, NodeMeasured <T> y)
{
var diff = x.Distance - y.Distance;
if (diff < 0)
{
return(-1);
}
else if (diff > 0)
{
return(1);
}
return(0);
}
private double invEarthDiameter = 1.0 / 12742018.0; /* meters */
/// <summary>
/// Return the n elements closes to the search element for a given startingNode, withing max kilometers
/// </summary>
/// <param name="search"></param>
/// <param name="startingNode"></param>
/// <param name="n">Return N elements</param>
/// <param name="max">Maxim distance to look for</param>
/// <returns></returns>
public List <NodeMeasured <T> > Lookup(T search, Node <T> node, int n, double max)
{
if (max > 0)
{
max = 2 * Math.Sin(max * invEarthDiameter);
//max = 10000;
}
var result = new List <NodeMeasured <T> >();
if (node == null || max <= 0 || n == 0)
{
return(result);
}
var stack = new Stack <object>();
stack.Push(node);
stack.Push(0.0);
while (stack.Count > 0)
{
double dist = (double)stack.Pop();
node = (Node <T>)stack.Pop();
if (node == null)
{
continue;
}
// If this subtree is further away than we care about, then skip it.
if (dist > max)
{
continue;
}
// If we've already found enough locations, and the furthest one is closer
// than this subtree possibly could be, just skip the subtree.
if (result.Count == n && result[result.Count - 1].Distance < dist * dist)
{
continue;
}
//Iterate all the way down the tree, adding nodes that we need to remember
//to visit later onto the stack.
var searchPosition = Position(search);
while (node != null)
{
Node <T> m;
if (searchPosition[node.Axis] < node.Split)
{
stack.Push(node.Right);
stack.Push(node.Split - searchPosition[node.Axis]);
m = node.Left;
}
else
{
stack.Push(node.Left);
stack.Push(searchPosition[node.Axis] - node.Split);
m = node.Right;
}
if (m != null)
{
node = m;
}
else
{
break;
}
}
// Once hit a leaf node, insert into the list of candidates, making sure the list keep sorted
dist = this.Distance(searchPosition, Position(node.Data));
if (dist <= max * max)
{
var candidate = new NodeMeasured <T>(node, dist);
var index = result.BinarySearch(candidate, new CompareByDistance <T>());
if (index < 0)
{
result.Insert(~index, candidate);
}
if (result.Count > n)
{
result.Remove(result.Last());
}
}
}
return(result);
}
