dijkstra优化

数据加强版的最短路

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

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <vector>
 5 #include <queue>
 6 using namespace std;
 7 typedef pair<int, int> PII;
 8 const int N   = 1e5 + 10;
 9 const int INF = 2147483647;
10 
11 int n, m, s;
12 int dist[N];
13 vector<PII> g[N];
14 int vis[N];
15 
16 void dijkstra()
17 {
18     memset(vis, 0, sizeof(vis));
19     for(int i = 1; i <= n; i++)    dist[i] = INF;
20     dist[s] = 0;
21     //优先队列 
22     priority_queue<PII> q;
23     q.push({0, s});
24     while(!q.empty())
25     {
26         int node = q.top().second;    q.pop();
27         if(vis[node] == 1)    continue;
28         vis[node] = 1;
29         for(int i = 0; i < g[node].size(); i++)
30         {
31             int tmpNode = g[node][i].second;
32             if(dist[tmpNode] > dist[node] + g[node][i].first)
33             {
34                 dist[tmpNode] = dist[node] + g[node][i].first;
35                 //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 
36                 q.push({-dist[tmpNode], tmpNode});        
37             }    
38         } 
39     }
40 }
41 
42 int main()
43 {
44     cin >> n >> m >> s;
45     for(int i = 1; i <= m; i++)
46     {
47         int u, v, d;
48         scanf("%d %d %d", &u, &v, &d);
49         g[u].push_back({d, v});
50     }
51     dijkstra();
52     for(int i = 1; i <= n; i++)
53         i==1?cout<<dist[i]:cout<<" "<<dist[i];
54     return 0;
55 }

 

posted @ 2019-10-18 23:44  nonameless  阅读(239)  评论(0)  编辑  收藏  举报