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/**
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* File: graph_bfs.c
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* Created Time: 2023-07-11
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* Author: NI-SW (947743645@qq.com)
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*/
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#include "graph_adjacency_list.c"
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// 假設節點最大數量為 100
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#define MAX_SIZE 100
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/* 節點佇列結構體 */
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typedef struct {
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Vertex *vertices[MAX_SIZE];
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int front, rear, size;
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} Queue;
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/* 建構子 */
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Queue *newQueue() {
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Queue *q = (Queue *)malloc(sizeof(Queue));
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q->front = q->rear = q->size = 0;
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return q;
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}
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/* 判斷佇列是否為空 */
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int isEmpty(Queue *q) {
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return q->size == 0;
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}
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/* 入列操作 */
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void enqueue(Queue *q, Vertex *vet) {
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q->vertices[q->rear] = vet;
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q->rear = (q->rear + 1) % MAX_SIZE;
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q->size++;
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}
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/* 出列操作 */
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Vertex *dequeue(Queue *q) {
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Vertex *vet = q->vertices[q->front];
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q->front = (q->front + 1) % MAX_SIZE;
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q->size--;
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return vet;
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}
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/* 檢查頂點是否已被訪問 */
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int isVisited(Vertex **visited, int size, Vertex *vet) {
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// 走訪查詢節點，使用 O(n) 時間
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for (int i = 0; i < size; i++) {
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if (visited[i] == vet)
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return 1;
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}
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return 0;
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}
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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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void graphBFS(GraphAdjList *graph, Vertex *startVet, Vertex **res, int *resSize, Vertex **visited, int *visitedSize) {
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// 佇列用於實現 BFS
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Queue *queue = newQueue();
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enqueue(queue, startVet);
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visited[(*visitedSize)++] = 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 (!isEmpty(queue)) {
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Vertex *vet = dequeue(queue); // 佇列首頂點出隊
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res[(*resSize)++] = 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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AdjListNode *node = findNode(graph, vet);
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while (node != NULL) {
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// 跳過已被訪問的頂點
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if (!isVisited(visited, *visitedSize, node->vertex)) {
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enqueue(queue, node->vertex); // 只入列未訪問的頂點
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visited[(*visitedSize)++] = node->vertex; // 標記該頂點已被訪問
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}
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node = node->next;
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}
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}
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// 釋放記憶體
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free(queue);
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}
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/* Driver Code */
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int main() {
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// 初始化無向圖
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int vals[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
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int size = sizeof(vals) / sizeof(vals[0]);
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Vertex **v = valsToVets(vals, size);
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Vertex *edges[][2] = {{v[0], v[1]}, {v[0], v[3]}, {v[1], v[2]}, {v[1], v[4]}, {v[2], v[5]}, {v[3], v[4]},
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{v[3], v[6]}, {v[4], v[5]}, {v[4], v[7]}, {v[5], v[8]}, {v[6], v[7]}, {v[7], v[8]}};
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int egdeSize = sizeof(edges) / sizeof(edges[0]);
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GraphAdjList *graph = newGraphAdjList();
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// 新增所有頂點和邊
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for (int i = 0; i < size; i++) {
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addVertex(graph, v[i]);
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}
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for (int i = 0; i < egdeSize; i++) {
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addEdge(graph, edges[i][0], edges[i][1]);
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}
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printf("\n初始化後，圖為\n");
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printGraph(graph);
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// 廣度優先走訪
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// 頂點走訪序列
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Vertex *res[MAX_SIZE];
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int resSize = 0;
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// 用於記錄已被訪問過的頂點
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Vertex *visited[MAX_SIZE];
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int visitedSize = 0;
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graphBFS(graph, v[0], res, &resSize, visited, &visitedSize);
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printf("\n廣度優先走訪（BFS）頂點序列為\n");
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printArray(vetsToVals(res, resSize), resSize);
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// 釋放記憶體
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delGraphAdjList(graph);
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free(v);
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return 0;
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}
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