最小生成树之PRIM-O(nlog2n)

来源：互联网发布：java大量线程wait状态编辑：程序博客网时间：2024/06/14 04:25

#include<stdio.h>#include<string.h>#include<stdlib.h>const int Maxn=30010,Maxm=120010,Inf=1000000000;int e,to[Maxm],ws[Maxm],begin[Maxn],next[Maxm];int d[Maxn],p[Maxn],q[Maxn],pos[Maxn];void add(int x,int y,int z){to[++e]=y;next[e]=begin[x];begin[x]=e;ws[e]=z;}int main(){freopen("prim.in","r",stdin);freopen("prim.out","w",stdout);int i,j,k,m,n,l;int x,y,z,u,v,w;scanf("%d%d",&n,&m);for(i=1;i<=m;i++){scanf("%d%d%d",&x,&y,&z);add(x,y,z);add(y,x,z);}for(i=1;i<=n;i++)d[i]=Inf;d[1]=0;l=n;for(i=1;i<=n;i++){q[i]=i;pos[i]=i;}int ans=0;for(i=1;i<=n;i++){k=q[1];q[1]=q[l];pos[q[l]]=1;l--;u=1;while( (u*2<=l && d[q[u]]>d[q[2*u]]) || (u*2+1<=l && d[q[u]]>d[q[2*u+1]]) ){v=u*2;if(v+1<=l && d[q[v]]>d[q[v+1]])v++;w=q[u];q[u]=q[v];q[v]=w;w=pos[q[u]];pos[q[u]]=pos[q[v]];pos[q[v]]=w;u=v;}p[k]=1;ans+=d[k];for(j=begin[k];j;j=next[j]){u=to[j];if(!p[u] && d[u]>ws[j])d[u]=ws[j];v=pos[u];while(v>=1 && d[q[v]]<d[q[v/2]]){w=q[v];q[v]=q[v/2];q[v/2]=w;w=pos[q[v]];pos[q[v]]=pos[q[v/2]];pos[q[v/2]]=w;v=v/2;}}}printf("%d\n",ans);return 0;}

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