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52 lines
1.9 KiB
52 lines
1.9 KiB
/**
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* File: graph_dfs.java
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* Created Time: 2023-02-12
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* Author: krahets (krahets@163.com)
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*/
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package chapter_graph;
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import java.util.*;
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import utils.*;
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public class graph_dfs {
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/* Depth-first traversal helper function */
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static void dfs(GraphAdjList graph, Set<Vertex> visited, List<Vertex> res, Vertex vet) {
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res.add(vet); // Record visited vertex
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visited.add(vet); // Mark the vertex as visited
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// Traverse all adjacent vertices of that vertex
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for (Vertex adjVet : graph.adjList.get(vet)) {
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if (visited.contains(adjVet))
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continue; // Skip already visited vertices
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// Recursively visit adjacent vertices
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dfs(graph, visited, res, adjVet);
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}
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}
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/* Depth-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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static List<Vertex> graphDFS(GraphAdjList graph, Vertex startVet) {
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// Vertex traversal sequence
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List<Vertex> res = new ArrayList<>();
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// Hash set, used to record visited vertices
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Set<Vertex> visited = new HashSet<>();
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dfs(graph, visited, res, startVet);
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return res;
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}
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public static void main(String[] args) {
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/* Initialize undirected graph */
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Vertex[] v = Vertex.valsToVets(new int[] { 0, 1, 2, 3, 4, 5, 6 });
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Vertex[][] edges = { { v[0], v[1] }, { v[0], v[3] }, { v[1], v[2] },
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{ v[2], v[5] }, { v[4], v[5] }, { v[5], v[6] } };
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GraphAdjList graph = new GraphAdjList(edges);
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System.out.println("\nAfter initialization, the graph is");
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graph.print();
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/* Depth-first traversal */
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List<Vertex> res = graphDFS(graph, v[0]);
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System.out.println("\nDepth-first traversal (DFS) vertex sequence is");
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System.out.println(Vertex.vetsToVals(res));
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}
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}
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