Add a better DFS solution

notes-and-examples/2026.07.21/main.py

@@ -1,24 +1,33 @@
 # Adjacency list
 first_graph = {
-    1: [3, 20],
+    1: [3, 20, 4, 5, 6],
     2: [20],
     3: [1, 20],
-    20: [2, 3]
+    20: [2, 3],
+    4: [1],
+    5: [1],
+    6: [1]
 }
 
 # First exercise: go from 1, to 20, to 2
 first_graph[first_graph[1][1]][0]
 
 # pass visited by reference
-def depth_first_search(graph: dict, start, visited=set()):
+def depth_first_search(graph: dict, start, visited=set(), traversal=list()):
-    print(start)
+    if start in visited:
+        return
+
+    visited.add(start)
+    traversal.append(start)
     if len(visited)==len(graph):
-        return visited
+        return
 
     for x in graph[start]:
-        if x not in visited:
+        depth_first_search(graph, x, visited, traversal)
-            visited.add(x)
-            return depth_first_search(graph, x, visited)
     
 
-depth_first_search(first_graph, 1)
+visited = set()
+traversal = list()
+depth_first_search(first_graph, 1, visited, traversal)
+print("Visited:", visited)
+print("Traversal:", traversal)