Dijkstra算法和前一篇的Prim算法非常像,區別就在於Dijkstra算法向最短路徑樹(SPT)中添加頂點的時候,是按照ta與源點的距離順序進行的。OSPF動態路由協議就是用的Dijkstra算法。下面還以那個圖的例子爲例:
代碼如下:
_=float('inf')
def dijkstra(graph,n):
dis=[0]*n
flag=[False]*n
pre=[0]*n
flag[0]=True
k=0
for i in range(n):
dis[i]=graph[k][i]
for j in range(n-1):
mini=_
for i in range(n):
if dis[i]<mini and not flag[i]:
mini=dis[i]
k=i
if k==0:#不連通
return
flag[k]=True
for i in range(n):
if dis[i]>dis[k]+graph[k][i]:
dis[i]=dis[k]+graph[k][i]
pre[i]=k
# print(k)
return dis,pre
if __name__=='__main__':
n=6
graph=[
[0,6,3,_,_,_],
[6,0,2,5,_,_],
[3,2,0,3,4,_],
[_,5,3,0,2,3],
[_,_,4,2,0,5],
[_,_,_,3,5,0],
]
dis,pre=dijkstra(graph,n)
print(dis)
print(pre)
輸出如下:
[0, 5, 3, 6, 7, 9]
[0, 2, 0, 2, 2, 3]
按照輸出結果用粗線表示最短路徑樹如下:
轉載請註明:轉自 http://blog.csdn.net/littlethunder/article/details/9748519