优化迪杰斯特拉

Posted 2020-09-19 秦时、长浩

 1 #include <cstdio>
 2 #include <queue>
 3 #include <cstring>
 4 #define Heap pair<int, int>
 5 //第一个int存的是到起点的距离，第二个int存的是点的编号
 6 
 7 using namespace std;
 8 
 9 const int INF = 2147483647;
10 int n, m, t, cnt;
11 int next[1000001], to[1000001], val[1000001], head[10001], dis[10001];
12 bool vis[1000001];
13 priority_queue <Heap, vector <Heap>, greater <Heap> > q;
14 //按照第一个int从小到大排序 
15 
16 inline void add(int a, int b, int c){
17     to[cnt] = b;
18     val[cnt] = c;
19     next[cnt] = head[a];
20     head[a] = cnt++;
21 }
22 
23 inline void Dijkstra(int s){//以s为起点 
24     int i, u, v;
25     Heap x;
26     for(i = 1; i <= n; i++) dis[i] = INF;
27     dis[s] = 0;
28     q.push(make_pair(0, s));//入队 
29     while(!q.empty()){
30         x = q.top();
31         q.pop();
32         u = x.second;
33         if(vis[u]) continue;//判断是否已经是最短路径上的点 
34         vis[u] = 1;
35         for(i = head[u]; i != -1; i = next[i]){//更新距离 
36             v = to[i];
37             if(dis[v] > dis[u] + val[i]){
38                 dis[v] = dis[u] + val[i];
39                 q.push(make_pair(dis[v], v));
40             }
41         }
42     }
43 }
44 
45 int main(){
46     int i, j, a, b, c, s;
47     scanf("%d %d %d", &n, &m, &s);
48     memset(head, -1, sizeof(head));
49     for(i = 1; i <= m; i++){
50         scanf("%d %d %d", &a, &b, &c);
51         add(a, b, c);
52     }
53     Dijkstra(s);
54     for(i = 1; i <= n; i++) printf("%d ", dis[i]);
55     return 0;
56 }

优化以后的

优化的迪杰斯特拉，推荐一下

但在某些情况下慢