Depth-first search (DFS) code in python

Question

Can you please let me know what is incorrect in below DFS code. It\'s giving correct result AFAIK, but I don\'t know when it will fail.

graph1 = {
    \'A\'          


        

Answer 1

Here's an iterative (non-recursive) implementation of a DFS:

def dfs_iterative(graph, start_vertex):
    visited = set()
    traversal = []
    stack = [start_vertex]
    while stack:
        vertex = stack.pop()
        if vertex not in visited:
            visited.add(vertex)
            traversal.append(vertex)
            stack.extend(reversed(graph[vertex]))   # add vertex in the same order as visited
    return traversal

test_graph = {
    'A' : ['B','S'],
    'B' : ['A'],
    'C' : ['D','E','F','S'],
    'D' : ['C'],
    'E' : ['C','H'],
    'F' : ['C','G'],
    'G' : ['F','S'],
    'H' : ['E','G'],
    'S' : ['A','C','G']
}

print(dfs_iterative(test_graph, 'A'))

Output:

['A', 'B', 'S', 'C', 'D', 'E', 'H', 'G', 'F']