#include<bits/stdc++.h>
#define PII pair<int,int>
using namespace std;

const int N=1e5+10;
int dis[N],hd[N],n,m,s,t,idx=1;
struct Glist{
	int to,w,nxt;
}e[N];
bool vis[N];

void add(int a,int b,int c)
{
	e[idx].w=c;
	e[idx].to=b;
	e[idx].nxt=hd[a];
	hd[a]=idx++; 
}

int Dijkstra()
{
	memset(dis,0x3f,sizeof(dis));
	dis[s]=0;
	priority_queue< PII,vector<PII>,greater<PII> >q;
	q.push( {0,s} );
	while(q.size())
	{
		PII t=q.top();
		int ver=t.second,dist=t.first;
		q.pop();
		
		if(vis[ver])continue;
		vis[ver]=1;
		
		for(int i=hd[ver];i!=-1;i=e[i].nxt)
		{
			int j=e[i].to;
			if(dis[j]>dis[ver]+e[i].w)
			{
				dis[j]=dis[ver]+e[i].w;
				q.push( {dis[j],j} );
			}
		}
	}
	if(dis[t]==0x3f3f3f3f)
	{
		cout<<"No Solution!";
		return -1;
	}
	return dis[t]; 
}

int main()
{
	cin>>n>>m>>s>>t;
	memset(hd,-1,sizeof(hd));
	for(int i=1;i<=m;++i)
	{
		int a,b,c;
		cin>>a>>b>>c;
		add(a,b,c);
		add(b,a,c);
	}
	cout<<Dijkstra();
	return 0;
} 

把模板改一下就好了

#include<bits/stdc++.h>

const int MaxN = 100010, MaxM = 500010;

struct edge
{
    int to, dis, next;
};

edge e[MaxM];
int head[MaxN], dis[MaxN], cnt;
bool vis[MaxN];
int n, m, s, endd;

inline void add_edge( int u, int v, int d )
{
    cnt++;
    e[cnt].dis = d;
    e[cnt].to = v;
    e[cnt].next = head[u];
    head[u] = cnt;
}

struct node
{
    int dis;
    int pos;
    bool operator <( const node &x )const
    {
        return x.dis < dis;
    }
};

std::priority_queue<node> q;


inline void dijkstra()
{
    dis[s] = 0;
    q.push( ( node ){0, s} );
    while( !q.empty() )
    {
        node tmp = q.top();
        q.pop();
        int x = tmp.pos, d = tmp.dis;
        if( vis[x] )
            continue;
        vis[x] = 1;
        for( int i = head[x]; i; i = e[i].next )
        {
            int y = e[i].to;
            if( dis[y] > dis[x] + e[i].dis )
            {
                dis[y] = dis[x] + e[i].dis;
                if( !vis[y] )
                {
                    q.push( ( node ){dis[y], y} );
                }
            }
        }
    }
}


int main()
{
    scanf( "%d%d%d%d", &n, &m, &s ,&endd );
    for(int i = 1; i <= n; ++i)dis[i] = 0x7fffffff;
    for( register int i = 0; i < m; ++i )
    {
        register int u, v, d;
        scanf( "%d%d%d", &u, &v, &d );
        add_edge( u, v, d );add_edge( v, u, d );
    }
    dijkstra();
    printf( "%d ", dis[endd] );
    return 0;
}