hello-algo/codes/cpp/chapter_graph/graph_dfs.cpp

/**
 * File: graph_dfs.cpp
 * Created Time: 2023-03-02
 * Author: Krahets (krahets@163.com)
 */

#include "../utils/common.hpp"
#include "./graph_adjacency_list.cpp"

/* 深度优先遍历 DFS 辅助函数 */
void dfs(GraphAdjList &graph, unordered_set<Vertex *> &visited, vector<Vertex *> &res, Vertex *vet) {
    res.push_back(vet);   // 记录访问顶点
    visited.emplace(vet); // 标记该顶点已被访问
    // 遍历该顶点的所有邻接顶点
    for (Vertex *adjVet : graph.adjList[vet]) {
        if (visited.count(adjVet))
            continue; // 跳过已被访问的顶点
        // 递归访问邻接顶点
        dfs(graph, visited, res, adjVet);
    }
}

/* 深度优先遍历 DFS */
// 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
vector<Vertex *> graphDFS(GraphAdjList &graph, Vertex *startVet) {
    // 顶点遍历序列
    vector<Vertex *> res;
    // 哈希表，用于记录已被访问过的顶点
    unordered_set<Vertex *> visited;
    dfs(graph, visited, res, startVet);
    return res;
}

/* Driver Code */
int main() {
    /* 初始化无向图 */
    vector<Vertex *> v = valsToVets(vector<int>{0, 1, 2, 3, 4, 5, 6});
    vector<vector<Vertex *>> edges = {{v[0], v[1]}, {v[0], v[3]}, {v[1], v[2]},
                                      {v[2], v[5]}, {v[4], v[5]}, {v[5], v[6]}};
    GraphAdjList graph(edges);
    cout << "\n初始化后，图为" << endl;
    graph.print();

    /* 深度优先遍历 DFS */
    vector<Vertex *> res = graphDFS(graph, v[0]);
    cout << "\n深度优先遍历（DFS）顶点序列为" << endl;
    printVector(vetsToVals(res));

    // 释放内存
    for (Vertex *vet : v) {
        delete vet;
    }

    return 0;
}