public int CompareTo(ValueIndexPair other)
{
if (Val < other.Val)
return -1;
if (Val > other.Val)
return 1;
return 0;
}
public BinaryHeap(int defCap)
{
_defaultCapacity = defCap;
_theArray = new ValueIndexPair[_defaultCapacity + 1];
// _theArray[0] serves as dummy Parent for root (who is at 1)
// "largest" is guaranteed to be larger than all keys in_ heap
_theArray[0] = new ValueIndexPair(double.PositiveInfinity, -1, -1);
_currentSize = 0;
}
public void Add(ValueIndexPair e)
{
// bubble up:
int where = _currentSize + 1; // new last place
while (e.CompareTo(_theArray[Parent(where)]) > 0)
{
_theArray[where] = _theArray[Parent(where)];
where = Parent(where);
}
_theArray[where] = e;
_currentSize++;
}
// returns pairs of indeces and -1,-1 if < K pairs
public int[,] GetKBestPairs(ParseForestItem[] items1, ParseForestItem[] items2)
{
// in_ this case K = items1.Length
var beenPushed = new bool[K,K];
var result = new int[K,2];
for (int i = 0; i < K; i++)
{
result[i, 0] = -1;
result[i, 1] = -1;
}
if (items1 == null || items2 == null || items1[0] == null || items2[0] == null)
return result;
var heap = new BinaryHeap(K + 1);
int n = 0;
var vip = new ValueIndexPair(items1[0].Prob + items2[0].Prob, 0, 0);
heap.Add(vip);
beenPushed[0, 0] = true;
while (n < K)
{
vip = heap.RemoveMax();
if (vip.Val == double.NegativeInfinity)
break;
result[n, 0] = vip.I1;
result[n, 1] = vip.I2;
n++;
if (n >= K)
break;
if (!beenPushed[vip.I1 + 1, vip.I2])
{
heap.Add(new ValueIndexPair(items1[vip.I1 + 1].Prob + items2[vip.I2].Prob, vip.I1 + 1, vip.I2));
beenPushed[vip.I1 + 1, vip.I2] = true;
}
if (!beenPushed[vip.I1, vip.I2 + 1])
{
heap.Add(new ValueIndexPair(items1[vip.I1].Prob + items2[vip.I2 + 1].Prob, vip.I1, vip.I2 + 1));
beenPushed[vip.I1, vip.I2 + 1] = true;
}
}
return result;
}