public IList <int[]> GetSkyline(int[,] buildings)
{
List <int[]> result = new List <int[]>();
if (buildings == null || buildings.GetLength(0) == 0 || buildings.GetLength(1) == 0)
{
return(result);
}
SkyLinePoint[] points = new SkyLinePoint[buildings.GetLength(0) * 2];
// Convert building left edge, right edge and height into points.
int index = 0;
for (var i = 0; i < buildings.GetLength(0); i++)
{
var x = buildings[i, 0];
var x2 = buildings[i, 1];
var y = buildings[i, 2];
points[index++] = new SkyLinePoint(x, y, true);
points[index++] = new SkyLinePoint(x2, y, false);
}
Array.Sort(points);
MaxHeap <int> heap = new MaxHeap <int>();
heap.Push(0);
int prevMax = 0;
foreach (var point in points)
{
if (point.IsStart)
{
heap.Push(point.Y);
int curMaxVal = heap.Peek();
if (curMaxVal > prevMax)
{
result.Add(new[] { point.X, point.Y });
prevMax = curMaxVal;
}
}
else
{
heap.Remove(point.Y);
int curMaxVal = heap.Peek();
if (curMaxVal < prevMax)
{
result.Add(new[] { point.X, curMaxVal });
prevMax = curMaxVal;
}
}
}
return(result);
}