translation: Add Python and Java code for EN version (#1345)

* Add the intial translation of code of all the languages

* test

* revert

* Remove

* Add Python and Java code for EN version

en/codes/python/chapter_graph/graph_dfs.py

@@ -0,0 +1,57 @@
+"""
+File: graph_dfs.py
+Created Time: 2023-02-23
+Author: krahets (krahets@163.com)
+"""
+
+import sys
+from pathlib import Path
+
+sys.path.append(str(Path(__file__).parent.parent))
+from modules import Vertex, vets_to_vals, vals_to_vets
+from graph_adjacency_list import GraphAdjList
+
+
+def dfs(graph: GraphAdjList, visited: set[Vertex], res: list[Vertex], vet: Vertex):
+    """Depth-first traversal helper function"""
+    res.append(vet)  # Record visited vertex
+    visited.add(vet)  # Mark the vertex as visited
+    # Traverse all adjacent vertices of that vertex
+    for adjVet in graph.adj_list[vet]:
+        if adjVet in visited:
+            continue  # Skip already visited vertices
+        # Recursively visit adjacent vertices
+        dfs(graph, visited, res, adjVet)
+
+
+def graph_dfs(graph: GraphAdjList, start_vet: Vertex) -> list[Vertex]:
+    """Depth-first traversal"""
+    # Use adjacency list to represent the graph, to obtain all adjacent vertices of a specified vertex
+    # Vertex traversal sequence
+    res = []
+    # Hash set, used to record visited vertices
+    visited = set[Vertex]()
+    dfs(graph, visited, res, start_vet)
+    return res
+
+
+"""Driver Code"""
+if __name__ == "__main__":
+    # Initialize undirected graph
+    v = vals_to_vets([0, 1, 2, 3, 4, 5, 6])
+    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]],
+    ]
+    graph = GraphAdjList(edges)
+    print("\nAfter initialization, the graph is")
+    graph.print()
+
+    # Depth-first traversal
+    res = graph_dfs(graph, v[0])
+    print("\nDepth-first traversal (DFS) vertex sequence is")
+    print(vets_to_vals(res))