public void ExtractRootMax()
{
PriorityQueue<int> q = new PriorityQueue<int>((i, j) => j.CompareTo(i));
q.Storage = new List<int> { 11, 5, 8, 3, 4 };
int max = q.ExtractRoot();
Assert.AreEqual(11, max);
Assert.AreEqual(4, q.Storage.Count);
Assert.AreEqual(8, q.Storage[0]);
Assert.AreEqual(4, q.Storage[2]);
}
/// <summary>
/// For given 'center' point returns a subset of 'm' stored points that are
/// closer to the center than others.
///
/// E.g. Stored: (0, 1) (0, 2) (0, 3) (0, 4) (0, 5)
///
/// Find(new Point(0, 0), 3) -> (0, 1), (0, 2), (0, 3)
///
/// Seems like we can do this in two ways
///
/// Quick select - as we do quick sort on distance from center point,
/// stop is pivot index == m, then everything on left is closest m
/// complexity will be n log n
///
/// Max - Heap - reprocess the points into a max - heap with bounded size of m
/// Since everything in heap is smaller than max value, this will also ensure we
/// get m closet points. complexity will be n log m
/// </summary>
/// <param name="point"></param>
/// <param name="k"></param>
public static List<int[]> Find(List<int[]> points, int[] centerPoint, int m)
{
PriorityQueue<int[]> maxHeap = new PriorityQueue<int[]>((i, j) =>
//since this is a max heap, we want to compare j against i
//and we are comparing distance (sqrt(x^2 + y^2)) from the point
(System.Math.Pow(j[0] - centerPoint[0], 2) + System.Math.Pow(j[1] - centerPoint[1], 2))
.CompareTo(System.Math.Pow(i[0] - centerPoint[0], 2) + System.Math.Pow(i[1] - centerPoint[1], 2))
);
foreach(int[] point in points) {
maxHeap.Add(point);
if (maxHeap.Storage.Count > m)
{
maxHeap.ExtractRoot();
}
}
List<int[]> result = new List<int[]>();
while(maxHeap.Storage.Count > 0)
{
result.Add(maxHeap.ExtractRoot());
}
return result;
}
public void ExtractRootMin()
{
PriorityQueue<int> q = new PriorityQueue<int>((i, j) => i.CompareTo(j));
q.Storage = new List<int> { 4, 4, 8, 9, 4, 12, 9, 11, 13 };
int min = q.ExtractRoot();
Assert.AreEqual(4, min);
Assert.AreEqual(8, q.Storage.Count);
Assert.AreEqual(4, q.Storage[0]);
Assert.AreEqual(4, q.Storage[1]);
Assert.AreEqual(13, q.Storage[4]);
}
