以下是从维基百科提取的伪代码:
function Dijkstra(Graph, source):
2 for each vertex v in Graph: // Initializations
3 dist[v] := infinity ; // Unknown distance function from source to v
4 previous[v] := undefined ; // Previous node in optimal path from source
5 end for ;
6 dist[source] := 0 ; // Distance from source to source
7 Q := the set of all nodes in Graph ; // All nodes in the graph are unoptimized - thus are in Q
8 while Q is not empty: // The main loop
9 u := vertex in Q with smallest distance in dist[] ; // Start node in first case
10 if dist[u] = infinity:
11 break ; // all remaining vertices are inaccessible from source
12 end if ;
13 remove u from Q ;
14 for each neighbor v of u: // where v has not yet been removed from Q.
15 alt := dist[u] + dist_between(u, v) ;
16 if alt < dist[v]: // Relax (u,v,a)
17 dist[v] := alt ;
18 previous[v] := u ;
19 decrease-key v in Q; // Reorder v in the Queue
20 end if ;
21 end for ;
22 end while ;
23 return dist[] ;
24 end Dijkstra.
现在,在第14行中,我们可以看到仅对
Q
中尚未删除的邻居u
应用松弛操作。但是,如果我们还考虑已从Q
中删除的u
的邻居,则我认为该算法确实适用于负权重。我没有找到任何与此主张相矛盾的实例。
那么,为什么迪杰斯特拉算法不会以这种方式改变呢?