优先队列dijkstra

#include<bits/stdc++.h>

using namespace std;

typedef pair<int,int> PII;

const int N = 1e6 + 10;

int n,m;
int h[N],w[N],e[N],ne[N],idx;
int dist[N];
bool st[N];

void add(int a,int b,int c)
{
    e[idx] = b,w[idx] = c,ne[idx] = h[a],h[a] = idx ++;
}

int dijkstra()
{
    memset(dist,0x3f,sizeof dist);
    dist[1] = 0;
    priority_queue<PII,vector<PII>,greater<PII>> heap;
    heap.push({0,1});//1是距离
    while(heap.size())
    {
        auto t = heap.top();
        heap.pop();
        int v = t.second;
        if(st[v])continue;
        st[v] = true;
        for(int i = h[v];i != -1;i = ne[i])
        {
            int j = e[i];
            if(dist[j] > dist[v] + w[i])
            {
                dist[j] = dist[v] + w[i];
                heap.push({dist[j],j});
            }
        }
    }
    if(dist[n] == 0x3f3f3f3f)return -1;
    return dist[n];
}
int main()
{
    cin >> n >> m;
    memset(h,-1,sizeof h);
    while(m --)
    {
        int a,b,c;
        cin >> a >> b >> c;
        add(a,b,c);
    }
    cout <<dijkstra();
    return 0;
}