基于python的dijkstra算法实现

以下是基于python的dijkstra算法实现代码：

import heapq

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

# example usage
graph = {
    'A': {'B': 2, 'C': 4},
    'B': {'D': 3},
    'C': {'D': 1, 'E': 5},
    'D': {'E': 1},
    'E': {}
}
print(dijkstra(graph, 'A'))

运行结果：

{'A': 0, 'B': 2, 'C': 4, 'D': 5, 'E': 6}

该代码实现了dijkstra算法，输入为一个图和起点，返回一个字典，其中键为节点，值为该节点到起点的距离。该算法使用了优先队列来优化寻找最短路径的过程。时间复杂度为O(ElogV)，其中E为边数，V为节点数。