/// <summary> /// Merges another CyclicForrest into the current one. /// </summary> internal void AddChildren(CyclicForrest <T> newChildren) => ConnectToCurrentCyclicList(newChildren.Rank, newChildren.FirstChild);
private void Consolidate()
{
if (root.IsEmpty)
{
Debug.Assert(numberOfElements == 0);
return;
}
// The maximum rank is log2(numberOfElements). +1 because the array is 0-based.
var n = CurrMaxRank;
FibNode <T>[] trees = new FibNode <T> [n];
// Create trees for a new heap forrest from the old heap forrest
{
var currTree = root.FirstChild;
do
{
var nextNode = currTree.NextSibling;
ProcessTree(trees, currTree);
currTree = nextNode;
} while (currTree != root.FirstChild);
}
// Create new heap forrest from the newly created trees with unique ranks
{
uint newHeapRank = 0;
FibNode <T> newHeapRoot = null;
FibNode <T> lastNewHeapNode = null;
for (int i = 0; i < trees.Length; i++)
{
FibNode <T> newTree = trees[i];
if (newTree == null)
{
continue;
}
AddTreeToNewHeap(ref newHeapRank, ref newHeapRoot, ref lastNewHeapNode, newTree);
}
lastNewHeapNode.NextSibling = newHeapRoot;
newHeapRoot.PreviousSibling = lastNewHeapNode;
root = new CyclicForrest <T>(newHeapRoot, newHeapRank);
}
Debug.Assert(root.CheckChildren());
//
// Below are only local functions. They are not inlined because I believe it's more readable this way since they all
// .. represent a standalone functionality. Others might disagree with that assesment, however.
//
// Connects a new tree to a heap forrest that is just being build
void AddTreeToNewHeap(ref uint rank, ref FibNode <T> firstNode, ref FibNode <T> lastNode, FibNode <T> tree)
{
rank++;
tree.Parent = null;
tree.Marked = false;
UpdateMinimum(tree);
if (firstNode == null)
{
firstNode = tree;
}
else
{
lastNode.NextSibling = tree;
tree.PreviousSibling = lastNode;
}
lastNode = tree;
}
// Takes a tree and tries to add it to a rank-indexed tree array. If there is more than
// ...one tree with the same rank it merges them and processes the newly created tree.
// While recursion might seeem as a problem it can't be deeper than the maximum rank possible (with each
// ...level the rank of currently processed tree increases by one) which is log2(number of elements).
void ProcessTree(FibNode <T>[] treesArray, FibNode <T> treeBeingAdded)
{
uint currRank = treeBeingAdded.Children.Rank;
var otherTree = treesArray[currRank];
if (otherTree == null)
{
treesArray[currRank] = treeBeingAdded;
}
else
{
// Remove the tree the currently processed one will get merged with
treesArray[currRank] = null;
var lighterTree = treeBeingAdded.Weight < otherTree.Weight ? treeBeingAdded : otherTree;
var heavierTree = treeBeingAdded.Weight < otherTree.Weight ? otherTree : treeBeingAdded;
FibNode <T> newTree = MergeTrees(lighterTree, heavierTree);
Debug.Assert(currRank + 1 == newTree.Children.Rank);
Debug.Assert(newTree.Children.Rank <= CurrMaxRank);
ProcessTree(treesArray, newTree);
}
}
FibNode <T> MergeTrees(FibNode <T> lighterTree, FibNode <T> heavierTree)
{
Debug.Assert(lighterTree.Children.Rank == heavierTree.Children.Rank);
Debug.Assert(lighterTree.Weight <= heavierTree.Weight && heavierTree != lighterTree);
logger.AddValue(1);
// Remove the heavier tree from its original context and add it as a new sibling under the lighter tree.
heavierTree.ResetSiblingsAndParentToATreeState();
heavierTree.Parent = lighterTree;
lighterTree.Children.AddSingleNode(heavierTree);
Debug.Assert(lighterTree.Children.Rank <= CurrMaxRank);
Debug.Assert(lighterTree.Children.CheckChildren());
Debug.Assert(!lighterTree.Children.IsEmpty);
return(lighterTree);
}
}
