dijkstra算法python实现

MAX_value = 999999


def dijkstra(graph, s):
    # 判断图是否为空，如果为空直接退出
    if graph is None:
        return None
    dist = [MAX_value]*len(graph)
    dist[s] = 0
    S = []
    Q = [i for i in range(len(graph))]
    dist_init = [i for i in graph[s]]
    while Q:
        u_dist = min([d for v, d in enumerate(dist_init) if v in Q])
        u = dist_init.index(u_dist)

        S.append(u)
        Q.remove(u)

        for v, d in enumerate(graph[u]):
            if 0 < d < MAX_value:
                if dist[v] > dist[u]+d:
                    dist[v] = dist[u]+d
                    dist_init[v] = dist[v]
    return dist


if __name__ == '__main__':
    graph_list = [ [0, 9, MAX_value, MAX_value, MAX_value, 14,15,MAX_value],
                    [9, 0, 24, MAX_value, MAX_value, MAX_value,MAX_value,MAX_value],
                    [MAX_value, 24, 0, 6, 2, 18,MAX_value,19],
                    [MAX_value, MAX_value, 6, 0, 11,MAX_value,MAX_value, 6],
                    [MAX_value,MAX_value, 2, 11, 0, 30,20, 16],
                    [14,MAX_value,18,MAX_value,30,0,5,MAX_value],
                    [15,MAX_value,MAX_value,MAX_value,20,5,0,44],
                    [MAX_value,MAX_value,19,6,16,MAX_value,44,0]]

    distance = dijkstra(graph_list, 0)
    print(distance)

右箭头，说明下是无向图。计算从s到t的最短距离

算法如下