star1.py

sampleData = """start-A
start-b
A-c
A-b
b-d
A-end
b-end
"""

# data = open("data.txt", "r", encoding="utf-8").read()
data = sampleData
lst = [line.split("-") for line in data.splitlines()]
edges = [[a, b] for a, b in lst if a != "end" and b != "start"]
edges += [[b, a] for a, b in lst if a != "start" and b != "end"]

def find_path_r(current_path, found_paths):
    current_node = current_path[-1]
    if current_node == "end":
        found_paths.append(current_path)
        return
    for edge in edges:
        if edge[0] == current_node:
            if edge[1].isupper() or edge[1] not in current_path:
                find_path_r(current_path + [edge[1]], found_paths)
            

def find_paths():
    """Find the all the paths from start to the end node"""
    found_paths = []
    find_path_r(["start"], found_paths)
    return found_paths

print(len(find_paths()))