This is already the standard stack based DFS? def dfs(graph, source): n = len(graph) visited = set() stack = [source] while stack:

This is already the standard stack based DFS? def dfs(graph, source): n = len(graph) visited = set() stack = [source] while stack: node = stack.pop() if node in visited: continue visited.add(node) for nbr in graph[node]: stack.append(nbr) So I don't know what all the confusion is about...