179 lines
4.2 KiB
C++
179 lines
4.2 KiB
C++
/* file name: dfs.c */
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/* 圖形的追蹤: 相鄰串列與蹤向優先搜尋法(DFS)*/
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#include <stdio.h>
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#include <stdlib.h>
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#define MAX_V 100 /*最大節點數*/
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#define TRUE 1
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#define FALSE 0
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/*定義資料結構*/
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typedef struct node_tag {
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int vertex;
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struct node_tag *link;
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} Node;
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Node *adjlist[MAX_V+1]; /*宣告相鄰串列*/
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int visited[MAX_V+1]; /*記錄頂點是否已拜訪*/
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int total_vertex;
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void build_adjlist(void);
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void show_adjlist(void);
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void show_weight_matrix(void);
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void dfs(int);
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Node *searchlast(Node *);
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int weight_matrix[MAX_V+1][MAX_V+1]; /* 儲存權重矩陣 */
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int main()
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{
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build_adjlist(); /*以相鄰串列表示圖形*/
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show_weight_matrix(); /*顯示權重矩陣*/
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show_adjlist(); /*顯示串列之資料*/
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puts("\n------Depth Fisrt Search------");
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dfs(1); /*圖形之蹤向優先搜尋，以頂點1為啟始頂點*/
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printf("\n");
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return 0;
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}
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void build_adjlist()
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{
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FILE *fptr;
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Node *node, *lastnode;
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int vi, vj, weight;
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char line[256];
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int line_count = 0;
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fptr = fopen("up_1.dat", "r");
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if (fptr == NULL) {
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perror("up_2.dat");
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exit(0);
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}
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// 計算總頂點數
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while (fgets(line, sizeof(line), fptr)) {
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line_count++;
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}
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total_vertex = line_count;
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rewind(fptr);
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// 初始化陣列及各串列啟始值
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for (vi = 1; vi <= total_vertex; vi++) {
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visited[vi] = FALSE;
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adjlist[vi] = (Node *)malloc(sizeof(Node));
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adjlist[vi]->vertex = vi;
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adjlist[vi]->link = NULL;
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}
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// 讀取上三角矩陣
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for (vi = 1; vi <= total_vertex; vi++) {
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/* 讀取該行的數值 */
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for (vj = vi ; vj <= total_vertex; vj++) {
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if (fscanf(fptr, "%d", &weight) != 1) {
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printf("Error reading weight at vi=%d, vj=%d\n", vi, vj);
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continue;
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}
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// 儲存權重到矩陣
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weight_matrix[vi][vj] = weight;
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weight_matrix[vj][vi] = weight; // 因為是無向圖，所以對稱儲存
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// 如果相鄰（weight = 1），則建立連結
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if (weight == 1) {
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// 加入 vi -> vj 的連結
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node = (Node *)malloc(sizeof(Node));
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node->vertex = vj;
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node->link = NULL;
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lastnode = searchlast(adjlist[vi]);
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lastnode->link = node;
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// 加入 vj -> vi 的連結（因為是無向圖）
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if (vi != vj) { // 避免自環
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node = (Node *)malloc(sizeof(Node));
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node->vertex = vi;
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node->link = NULL;
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lastnode = searchlast(adjlist[vj]);
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lastnode->link = node;
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}
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}
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}
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}
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fclose(fptr);
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}
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/*顯示各相鄰串列之資料*/
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void show_adjlist()
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{
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int index;
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Node *ptr;
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puts("Head adjacency nodes");
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puts("------------------------------");
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for (index = 1; index <= total_vertex; index++) {
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printf("V%-2d ",adjlist[index]->vertex);
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ptr = adjlist[index]->link;
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while (ptr != NULL) {
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printf("--> V%d ",ptr->vertex);
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ptr = ptr->link;
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}
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printf("\n");
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}
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}
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/* 修改顯示權重矩陣的函數，使其更清晰 */
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void show_weight_matrix()
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{
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int i, j;
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printf("\n=== Weight Matrix ===\n");
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printf(" ");
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for(j = 1; j <= total_vertex; j++) {
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printf("V%-3d", j);
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}
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printf("\n");
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for(i = 1; i <= total_vertex; i++) {
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printf("V%-3d", i);
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for(j = 1; j <= total_vertex; j++) {
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printf("%-4d", weight_matrix[i][j]);
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}
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printf("\n");
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}
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printf("\n");
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}
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/*圖形之蹤向優先搜尋*/
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void dfs(int v)
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{
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Node *ptr;
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int w;
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printf("V%d ",adjlist[v]->vertex);
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visited[v] = TRUE; /*設定v頂點為已拜訪過*/
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ptr = adjlist[v]->link; /*拜訪相鄰頂點*/
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do {
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/* 若頂點尚未走訪，則以此頂點為新啟始點繼續
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做蹤向優先搜尋法走訪，否則找與其相鄰的頂點
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直到所有相連接的節點都已走訪 */
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w = ptr->vertex;
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if (!visited[w])
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dfs(w);
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else
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ptr = ptr->link;
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} while (ptr != NULL);
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}
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/*搜尋串列最後節點函數*/
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Node *searchlast( Node *linklist )
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{
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Node *ptr;
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ptr = linklist;
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while (ptr->link != NULL)
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ptr = ptr->link;
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return ptr;
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}
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