堆优化的dijkstra

https://www.luogu.org/problem/show?pid=1339

#include<cstdio>
#include<queue>
#include<cstring>
#define N 55000
#define M 1000000
using namespace std;
int n,m,s,t,tot;
int nxt[M],to[M],front[N],cap[M];
int DIS[N];
bool vis[N];
struct edge
{
    int number,dis;
    bool operator <(edge b) const
    {
        return dis>b.dis;
    }
}now,nt;
priority_queue<edge>q;
void add(int u,int v,int w)
{
    to[++tot]=v; nxt[tot]=front[u]; front[u]=tot; cap[tot]=w;
    to[++tot]=u; nxt[tot]=front[v]; front[v]=tot; cap[tot]=w;
}
bool dijkstra()
{
    for(int i=1;i<=n;i++) DIS[i]=2e9;
    q.push((edge){s,0});
    DIS[s]=0;
    while(!q.empty())
    {
        now=q.top();q.pop();
        if(vis[now.number]) continue;
        vis[now.number]=true;
        for(int i=front[now.number];i;i=nxt[i])
        {
            if(DIS[to[i]]>DIS[now.number]+cap[i])
            {
                DIS[to[i]]=DIS[now.number]+cap[i];
                q.push((edge){to[i],DIS[to[i]]});
            }
        }
    }
    printf("%d",DIS[t]);
}

int main()
{
    int u,v,w;
    scanf("%d%d%d%d",&n,&m,&s,&t);
    while(m--)
    {
        scanf("%d%d%d",&u,&v,&w);
        add(u,v,w);
    }
    dijkstra();
}