查找图中的所有唯一路径并返回最便宜的路径

import heapq

def dijkstra(graph, start, end):
    queue = [(0, start, [])]
    seen = set()
    min_dist = defaultdict(int)
    while queue:
        (cost, node, path) = heapq.heappop(queue)
        if node not in seen:
            seen.add(node)
            path = path + [node]
            if node == end:
                return cost, path
            for c, neighbour in graph.get(node, []):
                if neighbour not in seen:
                    old_cost = min_dist.get(neighbour, None)
                    new_cost = cost + c
                    if old_cost is None or new_cost < old_cost:
                        min_dist[neighbour] = new_cost
                        heapq.heappush(queue, (new_cost, neighbour, path))
    return float("inf")

graph = {'A': [(2, 'B'), (3, 'C')],
         'B': [(1, 'C'), (3, 'D')],
         'C': [(2, 'D')],
         'D': [(2, 'E')],
         'E': []}

print(dijkstra(graph, 'A', 'D'))