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Change Dijkstra's algorithm to return all shortest distances

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This commit is contained in:
Stefan Müller 2025-05-14 20:53:39 +02:00
parent 73ead5aea7
commit 897bab12bf
2 changed files with 8 additions and 15 deletions
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2
include/aoc/common/WeightedEdgeGraph.hpp
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@ -28,7 +28,7 @@ class WeightedEdgeGraph
void addEdge(const int vertex1, const int vertex2, const int weight); void addEdge(const int vertex1, const int vertex2, const int weight);
int getVertexWeight(const int vertex) const; int getVertexWeight(const int vertex) const;
int getEdgeWeight(const int edge) const; int getEdgeWeight(const int edge) const;
int dijkstra(const int source, const int target) const; std::vector<int> dijkstra(const int source) const;
struct Incidence struct Incidence
{ {

21
src/common/WeightedEdgeGraph.cpp
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@ -49,7 +49,7 @@ int WeightedEdgeGraph::getEdgeWeight(const int edge) const
return edgeWeights_[edge]; return edgeWeights_[edge];
} }
int WeightedEdgeGraph::dijkstra(const int source, const int target) const std::vector<int> WeightedEdgeGraph::dijkstra(const int source) const
{ {
std::vector<int> distances(firstVertexIncidences_.size(), std::numeric_limits<int>::max()); std::vector<int> distances(firstVertexIncidences_.size(), std::numeric_limits<int>::max());
auto compare = [&distances](int left, int right) { return distances[left] > distances[right]; }; auto compare = [&distances](int left, int right) { return distances[left] > distances[right]; };
@ -63,25 +63,18 @@ int WeightedEdgeGraph::dijkstra(const int source, const int target) const
int v{ queue.top() }; int v{ queue.top() };
queue.pop(); queue.pop();
int incidence{ firstVertexIncidences_[v] }; for (auto neighbor = begin(v); neighbor != end(); ++neighbor)
while (incidence > -1)
{ {
int neighbor{ vertexEdgeIncidences_[incidence].vertex }; int newDistance{ distances[v] + edgeWeights_[neighbor->edge] };
int newDistance{ distances[v] + edgeWeights_[incidence >> 1] }; if (distances[neighbor->vertex] > newDistance)
if (distances[neighbor] > newDistance)
{ {
distances[neighbor] = newDistance; distances[neighbor->vertex] = newDistance;
queue.push(neighbor); queue.push(neighbor->vertex);
} }
if (neighbor == target)
{
return distances[target];
}
incidence = vertexEdgeIncidences_[incidence].next;
} }
} }
return -1; return distances;
} }
WeightedEdgeGraph::NeighborIterator WeightedEdgeGraph::begin(const int vertex) const WeightedEdgeGraph::NeighborIterator WeightedEdgeGraph::begin(const int vertex) const