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60 lines
2.1 KiB
60 lines
2.1 KiB
/**
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* File: graph_bfs.cpp
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* Created Time: 2023-03-02
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* Author: krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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#include "./graph_adjacency_list.cpp"
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/* Breadth-first traversal */
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// Use adjacency list to represent the graph, to obtain all adjacent vertices of a specified vertex
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vector<Vertex *> graphBFS(GraphAdjList &graph, Vertex *startVet) {
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// Vertex traversal sequence
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vector<Vertex *> res;
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// Hash set, used to record visited vertices
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unordered_set<Vertex *> visited = {startVet};
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// Queue used to implement BFS
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queue<Vertex *> que;
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que.push(startVet);
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// Starting from vertex vet, loop until all vertices are visited
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while (!que.empty()) {
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Vertex *vet = que.front();
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que.pop(); // Dequeue the vertex at the head of the queue
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res.push_back(vet); // Record visited vertex
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// Traverse all adjacent vertices of that vertex
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for (auto adjVet : graph.adjList[vet]) {
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if (visited.count(adjVet))
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continue; // Skip already visited vertices
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que.push(adjVet); // Only enqueue unvisited vertices
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visited.emplace(adjVet); // Mark the vertex as visited
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}
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}
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// Return the vertex traversal sequence
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return res;
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}
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/* Driver Code */
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int main() {
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/* Initialize undirected graph */
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vector<Vertex *> v = valsToVets({0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
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vector<vector<Vertex *>> edges = {{v[0], v[1]}, {v[0], v[3]}, {v[1], v[2]}, {v[1], v[4]},
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{v[2], v[5]}, {v[3], v[4]}, {v[3], v[6]}, {v[4], v[5]},
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{v[4], v[7]}, {v[5], v[8]}, {v[6], v[7]}, {v[7], v[8]}};
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GraphAdjList graph(edges);
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cout << "\nAfter initialization, the graph is\n";
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graph.print();
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/* Breadth-first traversal */
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vector<Vertex *> res = graphBFS(graph, v[0]);
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cout << "\nBreadth-first traversal (BFS) vertex sequence is" << endl;
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printVector(vetsToVals(res));
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// Free memory
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for (Vertex *vet : v) {
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delete vet;
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}
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return 0;
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}
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