HDU 1874 畅通工程续 dijkstra+priority_queue

#include<iostream>
#include<queue>
#include<algorithm>
#include<cstdio>
#include<stdlib.h>
//#include<bits/stdc++.h>
using namespace std;

const int maxn=1000+10;
const int inf=0x3f3f3f3f;
int n,m,dis[maxn],head[maxn],len;
bool vis[maxn];

struct edge{        //链式前向星所需的数据结构
    int to,val,next;
}e[maxn];

void add(int from,int to,int val){
       e[len].to=to;   //链式前向所需的加边
       e[len].val=val;
       e[len].next=head[from];
       head[from]=len++;
}

struct point{     //构造点的数据结构,为跑priority准备
      int val,id;
     point(int id,int val){
          this->id=id;
          this->val=val;
     }
    bool operator <(const point &x)const{
        return val>x.val;
      }
};

void dijkstra(int s){
       memset(vis,0,sizeof(vis));
       for(int i=0;i<n;i++)dis[i]=inf;
       priority_queue<point> q;
       q.push(point(s,0));
       dis[s]=0;
       while(!q.empty()){
             int cur=q.top().id;
             q.pop();
             if(vis[cur]) continue;//被标记过的点就不进队了,都对这个点贪心完了，就give up这个点了
             vis[cur]=true;
          for(int i=head[cur];i!=-1;i=e[i].next)
          {
               int id=e[i].to;
                if(!vis[id] && dis[cur]+e[i].val < dis[id])//松弛操作
                {
                      dis[id]=dis[cur]+e[i].val;
                      q.push(point(id,dis[id]));
                }
          }
     }
}

int main(){
     while(cin>>n>>m){
          len=0;
          memset(head,-1,sizeof(head));
          for(int i=0;i<m;i++)    //加边
          {
              int from,to,val;
              scanf("%d%d%d",&from,&to,&val);
              add(from,to,val);
              add(to,from,val);
          }

        int s,t;
          cin>>s>>t;             //源点,目的地
          dijkstra(s);
          if(dis[t]==inf)
              printf("-1\n");
          else
              printf("%d\n",dis[t]);
     }
    return 0;
}