Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_graph/graph_dfs.cpp

@@ -0,0 +1,55 @@
+/**
+ * File: graph_dfs.cpp
+ * Created Time: 2023-03-02
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+#include "./graph_adjacency_list.cpp"
+
+/* Depth-first traversal helper function */
+void dfs(GraphAdjList &graph, unordered_set<Vertex *> &visited, vector<Vertex *> &res, Vertex *vet) {
+    res.push_back(vet);   // Record visited vertex
+    visited.emplace(vet); // Mark the vertex as visited
+    // Traverse all adjacent vertices of that vertex
+    for (Vertex *adjVet : graph.adjList[vet]) {
+        if (visited.count(adjVet))
+            continue; // Skip already visited vertices
+        // Recursively visit adjacent vertices
+        dfs(graph, visited, res, adjVet);
+    }
+}
+
+/* Depth-first traversal */
+// Use adjacency list to represent the graph, to obtain all adjacent vertices of a specified vertex
+vector<Vertex *> graphDFS(GraphAdjList &graph, Vertex *startVet) {
+    // Vertex traversal sequence
+    vector<Vertex *> res;
+    // Hash set, used to record visited vertices
+    unordered_set<Vertex *> visited;
+    dfs(graph, visited, res, startVet);
+    return res;
+}
+
+/* Driver Code */
+int main() {
+    /* Initialize undirected graph */
+    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 << "\nAfter initialization, the graph is" << endl;
+    graph.print();
+
+    /* Depth-first traversal */
+    vector<Vertex *> res = graphDFS(graph, v[0]);
+    cout << "\nDepth-first traversal (DFS) vertex sequence is" << endl;
+    printVector(vetsToVals(res));
+
+    // Free memory
+    for (Vertex *vet : v) {
+        delete vet;
+    }
+
+    return 0;
+}