Add the Python codes for the chapter of Graph and Heap (#382)

codes/python/chapter_graph/graph_dfs.py

@@ -0,0 +1,48 @@
+"""
+File: graph_dfs.py
+Created Time: 2023-02-23
+Author: Krahets (krahets@163.com)
+"""
+
+import sys, os.path as osp
+sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
+from include import *
+from graph_adjacency_list import GraphAdjList
+
+
+""" 深度优先遍历 DFS 辅助函数 """
+def dfs(graph: GraphAdjList, visited: Set[Vertex], res: List[Vertex], vet: Vertex):
+    res.append(vet)     # 记录访问顶点
+    visited.add(vet) # 标记该顶点已被访问
+    # 遍历该顶点的所有邻接顶点
+    for adjVet in graph.adj_list[vet]:
+        if adjVet in visited:
+            continue # 跳过已被访问过的顶点
+        # 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
+def graph_dfs(graph: GraphAdjList, start_vet: Vertex) -> List[Vertex]:
+    # 顶点遍历序列
+    res = []
+    # 哈希表，用于记录已被访问过的顶点
+    visited = set()
+    dfs(graph, visited, res, start_vet)
+    return res
+
+
+""" Driver Code """
+if __name__ == "__main__":
+    # 初始化无向图
+    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("\n初始化后，图为")
+    graph.print()
+    
+    # 深度优先遍历 BFS
+    res = graph_dfs(graph, v[0])
+    print("\n深度优先遍历（DFS）顶点序列为")
+    print(vets_to_vals(res))