public int[][] KClosest(int[][] points, int K)
{
var heap = new MaxHeap(K);
int i = 1;
foreach (var point in points)
{
int distance = point[0] * point[0] + point[1] * point[1]; // SQRT
var node = new HeapNode();
node.distance = distance;
node.point = point;
if (i <= K)
{
heap.Push(node);
}
else
{
var max = heap.Peek().distance;
if (distance < max)
{
heap.Pop();
heap.Push(node);
}
}
i++;
}
int[][] res = new int[heap.Count][];
i = 0;
while (heap.Count > 0)
{
var node = heap.Pop();
res[i] = node.point;
i++;
}
return(res);
}
public HeapNode Pop()
{
if (Count == 0)
{
throw new Exception("There are no elements in the heap");
}
var nodeToReturn = arr[0];
arr[0] = arr[tail];
arr[tail] = null;
tail--;
int currentIndex = 0;
while (LeftLeafExists(currentIndex))
{
int biggest = GetLeftLeafIndex(currentIndex);
if (RigthLeafExists(currentIndex) && arr[GetRigthLeafIndex(currentIndex)].distance > arr[biggest].distance)
{
biggest = GetRigthLeafIndex(currentIndex);
}
if (arr[currentIndex].distance > arr[biggest].distance)
{
break;
}
// swap
HeapNode tmp = arr[biggest];
arr[biggest] = arr[currentIndex];
arr[currentIndex] = tmp;
currentIndex = biggest;
}
return(nodeToReturn);
}
public void Push(HeapNode node)
{
if (++tail >= arr.Length)
{
throw new Exception("Heap is full");
}
arr[tail] = node;
//
int currentIndex = tail;
int parentIndex = GetParent(currentIndex);
while (parentIndex >= 0 && arr[parentIndex].distance < arr[currentIndex].distance)
{
arr[currentIndex] = arr[parentIndex];
arr[parentIndex] = node;
currentIndex = parentIndex;
parentIndex = GetParent(currentIndex);
}
}
public MaxHeap(int size)
{
arr = new HeapNode[size];
}
