from collections import deque

def bfs(graph, start):
    visited = {start}
    queue = deque([start])
    order = []

    while queue:
        vertex = queue.popleft()
        order.append(vertex)
        for neighbor in graph[vertex]:
            if neighbor not in visited:
                visited.add(neighbor)
                queue.append(neighbor)

    return order

graph = {
    "A": ["B", "C"],
    "B": ["A", "D"],
    "C": ["A", "D"],
    "D": ["B", "C", "E"],
    "E": ["D"],
}

print(bfs(graph, "A"))  # ['A', 'B', 'C', 'D', 'E']