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#pragma once
#include <unordered_map>
namespace vcpkg::Graphs
{
enum class ExplorationStatus
{
// We have not visited this vertex
NOT_EXPLORED,
// We have visited this vertex but haven't visited all vertices in its subtree
PARTIALLY_EXPLORED,
// We have visited this vertex and all vertices in its subtree
FULLY_EXPLORED
};
template<class V, class U>
__interface AdjacencyProvider
{
std::vector<V> adjacency_list(const U& vertex) const;
U load_vertex_data(const V& vertex) const;
};
template<class V, class U>
static void topological_sort_internal(const V& vertex,
const AdjacencyProvider<V, U>& f,
std::unordered_map<V, ExplorationStatus>& exploration_status,
std::vector<U>& sorted)
{
ExplorationStatus& status = exploration_status[vertex];
switch (status)
{
case ExplorationStatus::FULLY_EXPLORED: return;
case ExplorationStatus::PARTIALLY_EXPLORED: Checks::exit_with_message(VCPKG_LINE_INFO, "cycle in graph");
case ExplorationStatus::NOT_EXPLORED:
{
status = ExplorationStatus::PARTIALLY_EXPLORED;
U vertex_data = f.load_vertex_data(vertex);
for (const V& neighbour : f.adjacency_list(vertex_data))
topological_sort_internal(neighbour, f, exploration_status, sorted);
sorted.push_back(std::move(vertex_data));
status = ExplorationStatus::FULLY_EXPLORED;
return;
}
default: Checks::unreachable(VCPKG_LINE_INFO);
}
}
template<class V, class U>
std::vector<U> topological_sort(const std::vector<V>& starting_vertices, const AdjacencyProvider<V, U>& f)
{
std::vector<U> sorted;
std::unordered_map<V, ExplorationStatus> exploration_status;
for (auto& vertex : starting_vertices)
{
topological_sort_internal(vertex, f, exploration_status, sorted);
}
return sorted;
}
}
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