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/**
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* File: graph_dfs.c
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* Created Time: 2023-07-13
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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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/* 哈希表 */
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typedef struct {
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unsigned int size;
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unsigned int *array;
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} HashTable;
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/* 初始化哈希表 */
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HashTable *newHash(unsigned int size) {
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HashTable *h = (HashTable *)malloc(sizeof(HashTable));
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h->array = (unsigned int *)malloc(sizeof(unsigned int) * size);
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memset(h->array, 0, sizeof(unsigned int) * size);
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h->size = size;
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return h;
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}
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/* 标记索引过的顶点 */
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void hashMark(HashTable *h, int index) {
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h->array[index % h->size] = 1;
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}
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/* 查询顶点是否已被标记 */
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int hashQuery(HashTable *h, int index) {
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// 若顶点已被标记，则返回 1
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if (h->array[index % h->size] == 1) {
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return 1;
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} else {
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return 0;
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}
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}
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/* 释放哈希表内存 */
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void freeHash(HashTable *h) {
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free(h->array);
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free(h);
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}
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/* 深度优先遍历 DFS 辅助函数 */
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int resIndex = 0;
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void dfs(GraphAdjList *graph, HashTable *visited, Vertex *vet, Vertex **res) {
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if (hashQuery(visited, vet->pos) == 1) {
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return; // 跳过已被访问过的顶点
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}
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hashMark(visited, vet->pos); // 标记顶点并将顶点存入数组
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res[resIndex] = vet; // 将顶点存入数组
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resIndex++;
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// 遍历该顶点链表
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Node *n = vet->list->head->next;
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while (n != 0) {
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// 递归访问邻接顶点
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dfs(graph, visited, n->val, res);
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n = n->next;
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}
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return;
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}
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/* 深度优先遍历 DFS */
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// 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
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Vertex **graphDFS(GraphAdjList *graph, Vertex *startVet) {
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// 顶点遍历序列
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Vertex **res = (Vertex **)malloc(sizeof(Vertex *) * graph->size);
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memset(res, 0, sizeof(Vertex *) * graph->size);
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// 哈希表，用于记录已被访问过的顶点
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HashTable *visited = newHash(graph->size);
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dfs(graph, visited, startVet, res);
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// 释放哈希表内存并将数组索引归零
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freeHash(visited);
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resIndex = 0;
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// 返回遍历数组
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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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GraphAdjList *graph = newGraphAdjList(10);
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for (int i = 0; i < 7; i++) {
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addVertex(graph, i);
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}
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addEdge(graph, 0, 1);
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addEdge(graph, 0, 3);
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addEdge(graph, 1, 2);
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addEdge(graph, 2, 5);
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addEdge(graph, 5, 4);
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addEdge(graph, 5, 6);
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printf("\n初始化后，图为:\n");
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printGraph(graph);
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// 深度优先遍历 DFS
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Vertex **vet = graphDFS(graph, graph->vertices[0]);
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// 输出遍历结果
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printf("\n深度优先遍历（DFS）顶点序列为\n");
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printf("[");
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printf("%d", vet[0]->val);
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for (int i = 1; i < graph->size && vet[i] != 0; i++) {
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printf(", %d", vet[i]->val);
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}
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printf("]\n");
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// 释放内存
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free(vet);
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return 0;
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}
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