【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。

 #include <cstdio>
 #include <queue>
 #include <cstring>
 #define heap pair<int, int>

 using namespace std;

 int n, m, cnt, ans;
 int head[], to[], next[], val[];
 bool vis[];
 priority_queue <heap, vector <heap>, greater <heap> > q;

 inline void add(int x, int y, int z)
 {
     to[cnt] = y;
     val[cnt] = z;
     next[cnt] = head[x];
     head[x] = cnt++;
 }

 inline void queue_prim()
 {
     int i, u, v, tot = n;
     heap x;
     q.push(make_pair(, ));
     while(!q.empty() && tot)
     {
         x = q.top();
         q.pop();
         u = x.second;
         if(vis[u]) continue;
         vis[u] = ;
         ans += x.first;
         tot--;
         for(i = head[u]; i != -; i = next[i])
         {
             v = to[i];
             if(!vis[v]) q.push(make_pair(val[i], v));
         }
     }
 }

 int main()
 {
     int i, x, y, z;
     memset(head, -, sizeof(head));
     scanf("%d %d", &n, &m);
     for(i = ; i <= m; i++)
     {
         scanf("%d %d %d", &x, &y, &z);
         add(x, y, z);
         add(y, x, z);
     }
     queue_prim();
     printf("%d", ans);
     return ;
 }