【模板】prim的heap优化

简单的代码。。

时间复杂度为O((n + m)logn)

大部分情况下还是跑不过kruskal的，慎用。

 1 #include <cstdio>
 2 #include <queue>
 3 #include <cstring>
 4 #define heap pair<int, int>
 5
 6 using namespace std;
 7
 8 int n, m, cnt, ans;
 9 int head[5001], to[400001], next[400001], val[400001];
10 bool vis[5001];
11 priority_queue <heap, vector <heap>, greater <heap> > q;
12
13 inline void add(int x, int y, int z)
14 {
15     to[cnt] = y;
16     val[cnt] = z;
17     next[cnt] = head[x];
18     head[x] = cnt++;
19 }
20
21 inline void queue_prim()
22 {
23     int i, u, v, tot = n;
24     heap x;
25     q.push(make_pair(0, 1));
26     while(!q.empty() && tot)
27     {
28         x = q.top();
29         q.pop();
30         u = x.second;
31         if(vis[u]) continue;
32         vis[u] = 1;
33         ans += x.first;
34         tot--;
35         for(i = head[u]; i != -1; i = next[i])
36         {
37             v = to[i];
38             if(!vis[v]) q.push(make_pair(val[i], v));
39         }
40     }
41 }
42
43 int main()
44 {
45     int i, x, y, z;
46     memset(head, -1, sizeof(head));
47     scanf("%d %d", &n, &m);
48     for(i = 1; i <= m; i++)
49     {
50         scanf("%d %d %d", &x, &y, &z);
51         add(x, y, z);
52         add(y, x, z);
53     }
54     queue_prim();
55     printf("%d", ans);
56     return 0;
57 }