72 lines
1.4 KiB
C++
72 lines
1.4 KiB
C++
class TopologicalSort
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{
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private:
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enum class STATUS
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{
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UN_VISITED,
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IN_SEARCHING,
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FINISHED
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};
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vector<vector<int>> edges;
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vector<STATUS> visited;
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vector<int> sequence;
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bool find_cycle = false; // cycle
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/**
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* @brief deep first search
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* @param[in] node index
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*
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*/
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void deepFirstSearch(int node)
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{
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visited[node] = STATUS::IN_SEARCHING;
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for (int neighbor : edges[node]) {
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if (visited[neighbor] == STATUS::UN_VISITED) {
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deepFirstSearch(neighbor);
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if (find_cycle) {
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return; // unsolvable
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}
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}
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else if (visited[neighbor] == STATUS::IN_SEARCHING) {
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find_cycle = true;
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return;
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}
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}
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visited[node] = STATUS::FINISHED;
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sequence.push_back(node);
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}
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public:
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/**
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* @brief topological sequence
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* @param[in] number of nodes
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* @param[in] node connection
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* @retval sequence
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*/
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vector<int> findTopologicalOrder(int numNodes, vector<vector<int>>& linkage)
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{
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edges.resize(numNodes);
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visited.resize(numNodes, STATUS::UN_VISITED);
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// generate adjacency list
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for (const auto& info : linkage) {
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edges[info[1]].push_back(info[0]);
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}
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// deep first search to determine the topological sequence
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for (int i = 0; i < numNodes && !find_cycle; ++i) {
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if (visited[i] == STATUS::UN_VISITED) {
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deepFirstSearch(i);
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}
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}
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if (find_cycle) {
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return vector<int>(); // unsolvable for cycle
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}
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reverse(sequence.begin(), sequence.end());
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return sequence;
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}
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}; |