SPFA算法 O(kE)

 1 //spfa
 2 
 3 #include<iostream>
 4 #include<cstdio> 
 5 #include<cstring>
 6 using namespace std;
 7 const int maxn=0x7f;
 8 bool vis[1001];
 9 int map[1001][1001],dis[1001],queue[1001],path[1001];
10 int n,m,head=0,tail=1,now;
11 
12 
13 void spfa(int x)
14 {
15     queue[head]=x;
16     vis[x]=true;
17     dis[x]=0;
18     path[x]=x;
19     while(head<tail)
20     {
21         now=queue[head];
22         for(int i=1;i<=n;i++)
23         {
24             if(dis[i]>dis[now]+map[now][i])
25             {
26                 dis[i]=dis[now]+map[now][i];
27                 path[i]=now;
28                 if(vis[i]==false)
29                 {
30                     queue[tail++]=i;
31                     vis[i]=true;
32                 }
33             }
34         }
35     vis[now]=false;
36     head++;
37     }
38 }
39 void print(int st,int en)
40 {
41     int q[1001];
42     int tot=1;
43     q[tot]=en;
44     tot++;
45     int temp=path[en];
46     while(temp!=st)
47     {
48         q[tot]=temp;
49         tot++;
50         temp=path[temp];
51     }
52     q[tot]=st;
53     for(int i=tot;i>=1;i--)
54     {
55         if(i!=1)
56           printf("%d -- >",q[i]);
57         else
58           printf("%d",q[i]);
59     }
60     cout<<endl;
61 }
62 int main()
63 {
64     memset(map,maxn,sizeof(map));
65     scanf("%d%d",&n,&m);
66     int he,ta,len;
67     for(int i=1;i<=m;i++)
68     {
69         cin>>he>>ta>>len;
70         map[he][ta]=map[ta][he]=len;
71     }
72     memset(dis,maxn,sizeof(dis));
73     memset(vis,false,sizeof(vis));
74     memset(queue,0,sizeof(queue));
75     int start,end;
76     scanf("%d%d",&start,&end);
77     spfa(start);
78     printf("%d\n",dis[end]);
79     print(start,end);
80     return 0;
81 }