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57 lines
1.8 KiB
Swift
57 lines
1.8 KiB
Swift
/**
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* File: graph_bfs.swift
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* Created Time: 2023-02-21
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* Author: nuomi1 (nuomi1@qq.com)
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*/
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import graph_adjacency_list_target
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import utils
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/* 廣度優先走訪 */
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// 使用鄰接表來表示圖，以便獲取指定頂點的所有鄰接頂點
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func graphBFS(graph: GraphAdjList, startVet: Vertex) -> [Vertex] {
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// 頂點走訪序列
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var res: [Vertex] = []
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// 雜湊集合，用於記錄已被訪問過的頂點
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var visited: Set<Vertex> = [startVet]
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// 佇列用於實現 BFS
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var que: [Vertex] = [startVet]
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// 以頂點 vet 為起點，迴圈直至訪問完所有頂點
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while !que.isEmpty {
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let vet = que.removeFirst() // 佇列首頂點出隊
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res.append(vet) // 記錄訪問頂點
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// 走訪該頂點的所有鄰接頂點
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for adjVet in graph.adjList[vet] ?? [] {
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if visited.contains(adjVet) {
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continue // 跳過已被訪問的頂點
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}
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que.append(adjVet) // 只入列未訪問的頂點
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visited.insert(adjVet) // 標記該頂點已被訪問
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}
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}
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// 返回頂點走訪序列
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return res
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}
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@main
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enum GraphBFS {
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/* Driver Code */
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static func main() {
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/* 初始化無向圖 */
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let v = Vertex.valsToVets(vals: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
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let edges = [
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[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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]
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let graph = GraphAdjList(edges: edges)
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print("\n初始化後，圖為")
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graph.print()
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/* 廣度優先走訪 */
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let res = graphBFS(graph: graph, startVet: v[0])
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print("\n廣度優先走訪（BFS）頂點序列為")
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print(Vertex.vetsToVals(vets: res))
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}
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}
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