用优先队列实现dijkstra算法

可以使用以下代码实现：

import heapq

def dijkstra(graph, start):
    distances = {node: float('inf') for node in graph}
    distances[start] = 0
    queue = [(0, start)]
    while queue:
        current_distance, current_node = heapq.heappop(queue)
        if current_distance > distances[current_node]:
            continue
        for neighbor, weight in graph[current_node].items():
            distance = current_distance + weight
            if distance < distances[neighbor]:
                distances[neighbor] = distance
                heapq.heappush(queue, (distance, neighbor))
    return distances

其中，graph是一个字典，表示图的邻接表，start是起点。这段代码使用了优先队列来实现dijkstra算法，可以在O(E log V)的时间内求出从起点到其它所有点的最短距离。