kruskal-边的贪心(并查集优化)-3

来源：互联网发布：珍珠控台软件编辑：程序博客网时间：2024/06/05 17:12
#include<bits/stdc++.h>using namespace std;const int N=1e4;int f[N+100],siz[N+100];int c[N+100];struct node{int u,v,w;}edge[N*20];bool cmp(node p,node q){return p.w<q.w;}void init(int n){for(int i=0;i<=n;i++) {f[i]=i;siz[i]=1;}}int found(int x){    while(x!=f[x])    {        f[x]=f[f[x]];        x=f[x];    }    return x;}void Union(int x,int y){    int tx=found(x);    int ty=found(y);    if(tx==ty) return;    if(siz[tx]>siz[ty]){f[ty]=tx;siz[tx]+=siz[ty];}    else {f[tx]=ty;siz[ty]+=siz[tx];}}int main(){    int n,m;    scanf("%d%d",&n,&m);    for(int i=0;i<m;i++) scanf("%d%d%d",&edge[i].u,&edge[i].v,&edge[i].w);    int cn=0;    for(int i=1,j=m;i<=n;i++)    {        scanf("%d",&c[i]);        if(c[i]!=-1)        {           edge[j].u=0,edge[j].v=i,edge[j++].w=c[i];           cn++;        }    }    sort(edge,edge+m+cn,cmp);    init(n);    int cost=0,flag=0,pcost;    for(int i=0;i<m+cn;i++)    {        int x=edge[i].u,y=edge[i].v;        int tx=found(x),ty=found(y);        if(edge[i].w<=0||tx!=ty)        {           Union(x,y);           if(x==0)           {            flag++;            if(flag==1){pcost=edge[i].w;}           }           cost+=edge[i].w;        }    }    if(flag==1) cost-=pcost;    int flag1=1;    for(int i=0;i<=n;i++) if(siz[i]>=n){flag1=0;break;}    if(flag1){printf("-1\n");return 0;}    printf("%d\n",cost);    return 0;}
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