最短路模板

//#pragma GCC optimize(3,"Ofast","inline")
//#include<unordered_map>
//#include<unordered_set>
#include<cstdio>
#include<iostream>
#include<cmath>
#include<functional>
#include<cstring>
#include<string>
#include<cstdlib>
#include<queue>
#include<map>
#include<algorithm>
#include<set>
#include<stack>
#include<vector>
#include<sstream>
#include<list>
using namespace std;
typedef long long ll;
const int INF=0x3f3f3f3f;
int mod=1000000007;
const int N=2e3+10;
const int maxn=1e7+10000;
int n,m;
int d[maxn],inq[maxn];
struct edge
{
    int from,to,len,next;
} e[maxn];
int num;
int head[maxn];
void add(int from,int to,int len)
{
    e[num]= {from,to,len,head[from]};
    head[from]=num++;
}
int s,t;
int spfa()
{
    queue<int>q;
    d[s]=0;
    q.push(s);
    inq[s]=1;
    while(!q.empty())
    {
        int now=q.front();
        q.pop();
        inq[now]=0;
        for(int i=head[now]; i!=-1; i=e[i].next)
        {
            int v=e[i].to;
            if(d[v]>d[now]+e[i].len)
            {
                d[v]=d[now]+e[i].len;
                if(inq[v])continue;
                inq[v]=1;
                q.push(v);
            }
        }
    }
    if(d[t]==INF)return -1;
    else return d[t];
}
int main()
{
    int n,m,x,y,l;
    while(cin>>n>>m)
    {
        memset(head,-1,sizeof head);
        memset(d,INF,sizeof d);
        memset(inq,0,sizeof inq);
        num=0;
        for(int i=1; i<=m; i++)
        {
            cin>>x>>y>>l;
            add(x,y,l);
            add(y,x,l);
        }
        cin>>s>>t;
        cout<<spfa()<<endl;
    }
    return 0;
}