acwing 堆优化版的dijkstar算法学习

#include<bits/stdc++.h>
using namespace std;
const int N=1e6+10;
int idx,e[N],ne[N],h[N],w[N];
bool st[N];
int dist[N];
int n,m;
typedef  pair<int,int>PII;
void add(int a,int b,int c)
{
    e[idx]=b;w[idx]=c;ne[idx]=h[a];h[a]=idx++;
}
int dijkstar()
{
    memset(dist,0x3f,sizeof dist);
    dist[1]=0;
    priority_queue<PII,vector<PII>,greater<PII>>heap;
    heap.push({0,1});
    while(heap.size())
    {
        auto t=heap.top();
        heap.pop();
        int ver=t.second;
        if(st[ver]) continue;
        st[ver]=1;
        for(int i=h[ver];i!=-1;i=ne[i])
        {
            int j=e[i];
            if(dist[j]>dist[ver]+w[i])
            {
                dist[j]=dist[ver]+w[i];
                heap.push({dist[j],j});
            }
        }
    }
    if(dist[n]==0x3f3f3f3f) return -1;
    else return dist[n];
}
int main()
{  
    memset(h,-1,sizeof h);
    cin>>n>>m;
    while(m--)
    {
        int a,b,c;
        cin>>a>>b>>c;
        add(a,b,c);
    }
    cout<<dijkstar()<<endl;
    return 0;
}