private BinaryTreeNode MergeNodesByWeightIntoOne(MinHeapUniversal <BinaryTreeNode> minHeap)
{
while (minHeap.GetHeapSize() != 1)
{
var firstSmallestNode = minHeap.ExtractMinElement();
var secondSmallestNode = minHeap.ExtractMinElement();
var superNode = new BinaryTreeNode();
superNode.SetKey(firstSmallestNode.GetKey() + secondSmallestNode.GetKey());
superNode.LeftChild = firstSmallestNode;
superNode.RightChild = secondSmallestNode;
minHeap.InsertElement(superNode);
}
return(minHeap.ExtractMinElement());
}
public int[] GetShortestPaths(Dictionary <int, NodeWeighted> graph, int startingVertex)
{
var visitedNodesCount = 1;
var closestUnvisitedNodes = new MinHeapUniversal <NodeWeighted>();
var pathLengths = new int[graph.Count + 1];
var firstNode = graph[startingVertex];
firstNode.Value = 0;
pathLengths[startingVertex] = 0;
var lastAddedNode = firstNode;
lastAddedNode.Visit();
while (visitedNodesCount++ != graph.Count - 1)
{
var unvisitedHeadNodes = lastAddedNode.Neighbours.FindAll(x => !x.Item1.IsVisited);
foreach (var nodeWeightTuple in unvisitedHeadNodes)
{
var(neighbour, edgeLength) = nodeWeightTuple;
var pathLength = edgeLength + lastAddedNode.Value;
var isNodeInHeap = neighbour.HeapIndex != 0;
if (isNodeInHeap)
{
closestUnvisitedNodes.TryDecreaseKey(neighbour.HeapIndex, pathLength);
}
else
{
neighbour.Value = pathLength;
closestUnvisitedNodes.InsertElement(neighbour);
}
}
if (closestUnvisitedNodes.GetHeapSize() != 0)
{
lastAddedNode = closestUnvisitedNodes.ExtractMinElement();
lastAddedNode.Visit();
lastAddedNode.HeapIndex = 0;
pathLengths[lastAddedNode.Id] = lastAddedNode.Value;
}
}
return(pathLengths);
}