18 C语言实现深度优先搜索

#include "stdio.h"
#include "stdlib.h"
#include "stdbool.h"

#define MaxVertex 10

typedef char ElemType;

typedef struct Node { //链表中的值
    int nextVertex;//指向的位置
    struct Node *next;
} Node;

struct HeadNode {//链表头
    ElemType data;
    struct Node *next;
};

typedef struct AdjacencyGraph {
    int vertexCount;//顶点数
    int edgeCount;//边数
    struct HeadNode vertex[MaxVertex];//顶点数组
} Graph;


Graph *create_graph() {
    Graph *graph = (Graph *) malloc(sizeof(Graph));
    if (graph == NULL) {
        exit(-1);
    }

    graph->vertexCount = 0;
    graph->edgeCount = 0;
    return graph;
}

void insert_vertex(Graph *graph, ElemType data) {
    if (graph->vertexCount >= MaxVertex) {
        return;
    }
    graph->vertex[graph->vertexCount].data = data;
    graph->vertex[graph->vertexCount].next = NULL;
    graph->vertexCount++;
}

void insert_edge(Graph *graph, int a, int b) {
    Node *node = graph->vertex[a].next;
    Node *newNode = malloc(sizeof(struct Node));
    newNode->next = NULL;
    newNode->nextVertex = b;

    if (node == NULL) {
        graph->vertex[a].next = newNode;
    } else {
        do {
            if (node->nextVertex == b) {
                free(newNode);
                break;
            }
            if (node->next) {
                node = node->next;
            } else {
                break;
            }
        } while (1);
        node->next = newNode;
    }

    graph->edgeCount++;
}

void printGraph(Graph *graph) {
    for (int i = 0; i < graph->vertexCount; ++i) {
        printf("%d | %c", i, graph->vertex[i].data);
        Node *node = graph->vertex[i].next;
        while (node) {
            printf(" -> %d", node->nextVertex);
            node = node->next;
        }

        putchar('\n');
    }
}

/**
 * 深度优先搜索
 * @param graph 图
 * @param start 开始顶点
 * @param target 结束顶点
 * @param visited 已经访问过的内容
 * @return
 */
bool dfs(Graph *graph, int start, int target, int *visited) {
    printf("%c -> ", graph->vertex[start].data);
    visited[start] = 1;
    if (start == target) {
        return true;
    }
    Node *node = graph->vertex[start].next;
    while (node) {
        if (visited[node->nextVertex] == 0) {
            if (dfs(graph, node->nextVertex, target, visited)) {
                return true;
            }
        }
        node = node->next;
    }

    return false;
}

int main() {
    setbuf(stdout, NULL);
    Graph *graph = create_graph();
    for (int i = 'A'; i <= 'F'; ++i) {
        insert_vertex(graph, (char) i);
    }
    insert_edge(graph, 0, 1);//A->B
    insert_edge(graph, 1, 2);//B->C
    insert_edge(graph, 1, 3);//B->D
    insert_edge(graph, 1, 4);//B->E
    insert_edge(graph, 4, 5);//E->F
    printGraph(graph);
    int arr[graph->vertexCount];
    for (int i = 0; i < graph->vertexCount; ++i) {
        arr[i] = 0;
    }
    printf("\n%d ", dfs(graph, 0, 5, arr));
    free(graph);
    return 0;
}

运行效果