CS412-Applied-Algorithms/Graph-Search/cs412_bus_stops_a.py

"""
name: Nicholas Tamassia

Honor Code and Acknowledgments:

        This work complies with the JMU Honor Code.

       Comments here on your code and submission.
"""

from collections import defaultdict, deque


def whatever_first_search(graph: dict[str, set[str]], start: str, stop: str):

    bag: deque[tuple[str | None, str]] = deque()
    bag.append((None, start))
    visited: set[str] = set()
    parent: dict[str, str | None] = {}

    while len(bag) != 0:
        parent_node, u = bag.pop()
        if u in visited:
            continue
        visited.add(u)
        parent[u] = parent_node

        if u == stop:
            path: list[str] = []
            while u is not None:
                path.append(u)
                u = parent[u]
            path.reverse()
            return path

        for v in graph[u]:
            if v not in visited:
                bag.append((u, v))

    return None


# All modules for CS 412 must include a main method that allows it
# to imported and invoked from other python scripts
def main():
    n: int = int(input())

    graph: dict[str, set[str]] = defaultdict(set)

    for _ in range(0, n):
        u, v = input().split()
        graph[u].add(v)
        graph[v].add(u)

    target = input().split()

    path = whatever_first_search(graph, target[0], target[1])

    if path is None:
        print("no route possible")
    else:
        print(" ".join(path))


if __name__ == "__main__":
    main()