P2683 小岛

spfa，

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 #define maxn 1000000
 4 #define inf 1<<30
 5 #define LL long long
 6 int n,m,s,num,t,head[maxn],dis[maxn],if_;
 7 struct Edge{
 8     int v,d,next;
 9 }edge[maxn];
10
11 void ins(int u,int v,int d)
12 {
13     edge[++num].v=v;
14     edge[num].d=d;
15     edge[num].next=head[u];
16     head[u]=num;
17 }
18
19 void spfa(int s)
20 {
21     queue<int>que;
22     bool vis[maxn];
23     memset(vis,false,sizeof(vis));
24     for(int i=1;i<=n;i++) dis[i]=inf;
25     dis[s]=0; vis[s]=1;
26     que.push(s);
27     while(!que.empty())
28     {
29         int cur=que.front();
30         que.pop();
31         for(int i=head[cur];i;i=edge[i].next)
32         {
33             if(dis[cur]+edge[i].d<dis[edge[i].v])
34             {
35                 dis[edge[i].v]=dis[cur]+edge[i].d;
36                 if(!vis[edge[i].v])
37                 {
38                     vis[edge[i].v]=1;
39                     que.push(edge[i].v);
40                 }
41             }
42         }
43         vis[cur]=false;
44      }
45 }
46
47 int main()
48 {
49     scanf("%d%d",&n,&m);
50     for(int i=1;i<=m;i++)
51     {
52         int u,v,d;
53         scanf("%d",&if_);
54         if(if_==1)
55         {
56             scanf("%d%d%d",&u,&v,&d);
57             ins(u,v,d); ins(v,u,d);
58         }
59         else{
60             scanf("%d%d",&s,&t);
61             spfa(s);
62             printf("%d\n",dis[t]==inf?-1:dis[t]);
63         }
64     }
65     return 0;
66 }