Constructing Roads(spfa)

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2493

 #include <stdio.h>
 #include <string.h>
 #include <queue>
 using namespace std;
 const int maxn=;
 const int maxm=maxn*maxn;
 const long long INF=1LL<<;
 int vis[maxn],head[maxn];
 int n,m,cnt = ;
 struct node
 {
     int u,v;
     long long w;
     int next;

 } edge[maxm];

 inline void add(int u,int v,long long w)
 {
     edge[cnt].u = u;
     edge[cnt].v = v;
     edge[cnt].w = w;
     edge[cnt].next = head[u];
     head[u] = cnt++;
 }

 void spfa(int s, long long dis[])
 {

     queue<int>q;
     q.push(s);
     vis[s] = ;
     dis[s] = ;
     while(!q.empty())
     {
         int u = q.front();
         q.pop();
         vis[u] = ;
         for (int j = head[u]; j!=-; j= edge[j].next)
         {
             int v = edge[j].v;
             long long w = edge[j].w;
             if (dis[u]+w < dis[v])
             {
                 dis[v] = dis[u]+w;
                 q.push(v);
                 vis[v] = ;
             }
         }
     }

 }
 void init()
 {

 }
 int main()
 {
     int u,v;
     long long w;
     long long dis1[maxn],dis2[maxn];
     while(~scanf("%d %d",&n,&m))
     {
         for (int i = ; i <= n; i++)
         {
             vis[i] = ;
             dis1[i] = INF;
             dis2[i] = INF;
             head[i] = -;
         }
         cnt = ;
         for (int i = ; i < m; i++)
         {
             scanf("%d %d %lld",&u,&v,&w);
             add(u,v,w);
             add(v,u,w);
         }
         int s,e;
         long long min=INF;
         scanf("%d %d",&s,&e);
         spfa(s,dis1);//求出起点到所有点的最短路径
         spfa(e,dis2);//求出终点到所有点的最短路径
         for (int i = ; i < cnt; i++)//遍历所有的边
         {
             u = edge[i].u;
             v = edge[i].v;
             w = edge[i].w;
             if (dis1[u]+dis2[v]+w/ < min)//S->u+e->v+w/2即为改变后的权值，找出最小的
                 min = dis1[u]+dis2[v]+w/;
         }
         if(min==INF)
         {
             puts("No solution");
             continue;
         }
         printf("%lld\n",min);
     }
     return ;
 }