UpdateValue
(
TKey existingKey,
TValue newValue
)
{
AssertValid();
const String MethodName = "UpdateValue";
Int32 iExistingItemIndex =
GetExistingItemIndex(existingKey, MethodName);
BinaryHeapItem <TKey, TValue> oExistingItem =
m_oItems[iExistingItemIndex];
TValue oExistingValue = oExistingItem.Value;
oExistingItem.Value = newValue;
Int32 iComparison =
m_oValueComparer.Compare(newValue, oExistingValue);
if (iComparison > 0)
{
SiftUp(iExistingItemIndex);
}
else if (iComparison < 0)
{
SiftDown(iExistingItemIndex);
}
AssertValid();
}
TryGetLeftOrRightChild
(
Int32 iItemIndex,
Boolean bLeftChild,
out BinaryHeapItem <TKey, TValue> oLeftOrRightChildItem,
out Int32 iLeftOrRightChildIndex
)
{
Debug.Assert(iItemIndex >= 0);
Debug.Assert(iItemIndex < m_oItems.Count);
AssertValid();
iLeftOrRightChildIndex = 2 * iItemIndex + (bLeftChild ? 1 : 2);
oLeftOrRightChildItem = null;
if (iLeftOrRightChildIndex < m_oItems.Count)
{
oLeftOrRightChildItem = m_oItems[iLeftOrRightChildIndex];
return(true);
}
iLeftOrRightChildIndex = Int32.MinValue;
return(false);
}
Add
(
TKey key,
TValue value
)
{
AssertValid();
// Add an item at the bottom of the tree.
BinaryHeapItem <TKey, TValue> oItem =
new BinaryHeapItem <TKey, TValue>(key, value);
m_oItems.Add(oItem);
Int32 iItemIndex = m_oItems.Count - 1;
m_oItemDictionary.Add(key, iItemIndex);
// Sift up from the bottom.
SiftUp(iItemIndex);
AssertValid();
}
TryGetRightChild
(
Int32 iItemIndex,
out BinaryHeapItem <TKey, TValue> oRightChildItem,
out Int32 iRightChildIndex
)
{
Debug.Assert(iItemIndex >= 0);
Debug.Assert(iItemIndex < m_oItems.Count);
AssertValid();
return(TryGetLeftOrRightChild(iItemIndex, false,
out oRightChildItem, out iRightChildIndex));
}
Remove
(
TKey key
)
{
AssertValid();
Int32 iRemovedItemIndex;
if (!m_oItemDictionary.TryGetValue(key, out iRemovedItemIndex))
{
// The item doesn't exist.
return;
}
BinaryHeapItem <TKey, TValue> oRemovedItem =
m_oItems[iRemovedItemIndex];
Int32 iItems = m_oItems.Count;
Int32 iLastItemIndex = iItems - 1;
BinaryHeapItem <TKey, TValue> oLastItem = m_oItems[iLastItemIndex];
// Swap the specified item with the last item.
SwapItems(iRemovedItemIndex, iLastItemIndex);
// Remove the last item and update the item dictionary.
m_oItems.RemoveAt(iLastItemIndex);
m_oItemDictionary.Remove(oRemovedItem.Key);
if (iRemovedItemIndex != iLastItemIndex)
{
Int32 iComparison =
m_oValueComparer.Compare(oLastItem.Value, oRemovedItem.Value);
if (iComparison > 0)
{
SiftUp(iRemovedItemIndex);
}
else if (iComparison < 0)
{
SiftDown(iRemovedItemIndex);
}
}
AssertValid();
}
RemoveTop()
{
AssertValid();
const String MethodName = "RemoveTop";
Int32 iItems = m_oItems.Count;
if (iItems == 0)
{
Debug.Assert(false);
throw new InvalidOperationException(String.Format(
"{0}.{1}: The heap is empty.",
this.ClassName,
MethodName
));
}
BinaryHeapItem <TKey, TValue> oRemovedItem = m_oItems[0];
Int32 iLastItemIndex = iItems - 1;
// Swap the first item with the last item.
SwapItems(0, iLastItemIndex);
// Remove the last item and update the item dictionary.
m_oItems.RemoveAt(iLastItemIndex);
m_oItemDictionary.Remove(oRemovedItem.Key);
if (m_oItems.Count > 0)
{
// Sift down from the top.
SiftDown(0);
}
AssertValid();
return(oRemovedItem);
}
TryGetTop
(
out BinaryHeapItem <TKey, TValue> top
)
{
AssertValid();
top = null;
if (m_oItems.Count == 0)
{
return(false);
}
top = m_oItems[0];
return(true);
}
SwapItems
(
Int32 iItem1Index,
Int32 iItem2Index
)
{
Debug.Assert(iItem1Index >= 0);
Debug.Assert(iItem1Index < m_oItems.Count);
Debug.Assert(iItem2Index >= 0);
Debug.Assert(iItem2Index < m_oItems.Count);
AssertValid();
BinaryHeapItem <TKey, TValue> oItem1 = m_oItems[iItem1Index];
BinaryHeapItem <TKey, TValue> oItem2 = m_oItems[iItem2Index];
m_oItems[iItem1Index] = oItem2;
m_oItems[iItem2Index] = oItem1;
m_oItemDictionary[oItem1.Key] = iItem2Index;
m_oItemDictionary[oItem2.Key] = iItem1Index;
}
SiftUp
(
Int32 iItemIndex
)
{
Debug.Assert(iItemIndex >= 0);
Debug.Assert(iItemIndex < m_oItems.Count);
AssertValid();
if (iItemIndex == 0)
{
return;
}
BinaryHeapItem <TKey, TValue> oItem = m_oItems[iItemIndex];
Int32 iParentIndex;
BinaryHeapItem <TKey, TValue> oParentItem;
while (TryGetParent(iItemIndex, out oParentItem, out iParentIndex))
{
// Compare the item with its parent.
if (m_oValueComparer.Compare(oParentItem.Value, oItem.Value) >= 0)
{
// The heap property is satisfied.
break;
}
// Swap the item with its parent.
SwapItems(iItemIndex, iParentIndex);
iItemIndex = iParentIndex;
}
}
TryGetParent
(
Int32 iItemIndex,
out BinaryHeapItem <TKey, TValue> oParentItem,
out Int32 iParentIndex
)
{
Debug.Assert(iItemIndex >= 0);
Debug.Assert(iItemIndex < m_oItems.Count);
AssertValid();
iParentIndex = Int32.MinValue;
oParentItem = null;
if (iItemIndex == 0)
{
return(false);
}
iParentIndex = (iItemIndex - 1) / 2;
oParentItem = m_oItems[iParentIndex];
return(true);
}
SiftDown
(
Int32 iItemIndex
)
{
Debug.Assert(iItemIndex >= 0);
Debug.Assert(iItemIndex < m_oItems.Count);
AssertValid();
BinaryHeapItem <TKey, TValue> oItem = m_oItems[iItemIndex];
while (true)
{
BinaryHeapItem <TKey, TValue> oLeftChildItem;
Int32 iLeftChildIndex;
if (!TryGetLeftChild(iItemIndex, out oLeftChildItem,
out iLeftChildIndex))
{
// We're at the bottom of the tree.
break;
}
// Assume that we need to compare the parent to its left child.
Int32 iChildItemIndexToCompareTo = iLeftChildIndex;
BinaryHeapItem <TKey, TValue> oChildItemToCompareTo =
oLeftChildItem;
BinaryHeapItem <TKey, TValue> oRightChildItem;
Int32 iRightChildIndex;
if (TryGetRightChild(iItemIndex, out oRightChildItem,
out iRightChildIndex))
{
if (m_oValueComparer.Compare(oRightChildItem.Value,
oLeftChildItem.Value) >= 0)
{
// We need to compare the parent to its right child.
oChildItemToCompareTo = oRightChildItem;
iChildItemIndexToCompareTo = iRightChildIndex;
}
}
if (m_oValueComparer.Compare(oItem.Value,
oChildItemToCompareTo.Value) >= 0)
{
// The heap property is satisfied.
break;
}
// Swap the item with its left or right child.
SwapItems(iItemIndex, iChildItemIndexToCompareTo);
iItemIndex = iChildItemIndexToCompareTo;
}
}
