dijkstra优化

数据加强版的最短路

洛谷链接：https://www.luogu.org/problem/P4779

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
typedef pair<int, int> PII;
const int N   = 1e5 + 10;
const int INF = 2147483647;

int n, m, s;
int dist[N];
vector<PII> g[N];
int vis[N];

void dijkstra()
{
    memset(vis, 0, sizeof(vis));
    for(int i = 1; i <= n; i++)    dist[i] = INF;
    dist[s] = 0;
    //优先队列 
    priority_queue<PII> q;
    q.push({0, s});
    while(!q.empty())
    {
        int node = q.top().second;    q.pop();
        if(vis[node] == 1)    continue;
        vis[node] = 1;
        for(int i = 0; i < g[node].size(); i++)
        {
            int tmpNode = g[node][i].second;
            if(dist[tmpNode] > dist[node] + g[node][i].first)
            {
                dist[tmpNode] = dist[node] + g[node][i].first;
                //注意，这里是把距离的负数压入队列，因为是大根堆，这样最短距离就在队首了 
                q.push({-dist[tmpNode], tmpNode});        
            }    
        } 
    }
}

int main()
{
    cin >> n >> m >> s;
    for(int i = 1; i <= m; i++)
    {
        int u, v, d;
        scanf("%d %d %d", &u, &v, &d);
        g[u].push_back({d, v});
    }
    dijkstra();
    for(int i = 1; i <= n; i++)
        i==1?cout<<dist[i]:cout<<" "<<dist[i];
    return 0;
}