private void ShiftUp(int k)
{
while (k > 1 && _items[k].CompareTo(_items[k / 2]) < 0)
{
HeapHelper.Swap <T>(_items, k, k / 2);
k = k / 2;
}
}
public T ExtractTop()
{
if (_count < 1)
{
return(null);
}
var top = _items[1];
HeapHelper.Swap <T>(_items, 1, _count);
_count--;
ShiftDown(1);
return(top);
}
private void ShiftDown(int k)
{
while (2 * k < _count)
{
var toBeSwapIndex = 2 * k;
if (2 * k + 1 <= _count && _items[2 * k + 1].CompareTo(_items[2 * k]) < 0)
{
toBeSwapIndex = 2 * k + 1;
}
if (_items[k].CompareTo(_items[toBeSwapIndex]) < 0)
{
break;
}
HeapHelper.Swap <T>(_items, k, toBeSwapIndex);
k = toBeSwapIndex;
}
}