hdu 4081 最小生成树变形

来源：互联网发布：塞尼斯托知乎编辑：程序博客网时间：2024/06/14 01:44
/*关于最小生成树的等效边，就是讲两个相同的集合连接在一起  先建立一个任意最小生成树，这条边分开的两个子树的节点最大的一个和为A，sum为最小生成树的权值和，B为sum-当前边的权值  不断枚举最小生成树中的边找最优值即可。*/#include<stdio.h>#include<string.h>#include<math.h>#include<stdlib.h>#define N  1100struct nodee{    int u,v;    double w;} edge[N*N];struct node{    int u,v,next;    double w;} bian[N*N];int index,yong,head[N],visit[N],n,pre[N],flag[N],c[N],aa[N],bb[N];double ans;double sum;void init(){    index=0;    yong=0;    sum=0;    int i;    for(i=1; i<=n; i++)        pre[i]=i;    memset(head,-1,sizeof(head));    memset(flag,0,sizeof(flag));}int cmp(const void *a,const void *b){    return (*(struct nodee *)a).w>(*(struct nodee *)b).w?1:-1;}double distance(int u,int v){    return sqrt(1.0*(aa[u]-aa[v])*(aa[u]-aa[v])+(bb[u]-bb[v])*(bb[u]-bb[v])*1.0);}int find(int x){    if(pre[x]!=x)        pre[x]=find(pre[x]);    return pre[x];}void addedge(int u,int v,double w){    bian[yong].u=u;    bian[yong].v=v;    bian[yong].w=w;    bian[yong].next=head[u];    head[u]=yong++;}void creat(){    int k=0,i;    for(i=0; i<index&&k<n-1; i++)    {        int u=find(edge[i].u);        int v=find(edge[i].v);        if(u!=v)        {            k++;            flag[k]=i;            sum=sum+edge[i].w;            addedge(edge[i].u,edge[i].v,edge[i].w);            addedge(edge[i].v,edge[i].u,edge[i].w);            pre[u]=v;        }    }    return ;}void dfs(int u)//定义全局变量好点{    int i;    visit[u]=1;    for(i=head[u]; i!=-1; i=bian[i].next)    {        int v=bian[i].v;        if(!visit[v])        {            dfs(v);        }    }    if(ans<c[u])        ans=c[u];}int main(){    int t,i,j;    double m;    scanf("%d",&t);    while(t--)    {        scanf("%d",&n);        init();        for(i=1; i<=n; i++)            scanf("%d%d%d",&aa[i],&bb[i],&c[i]);        for(i=1; i<n; i++)            for(j=i+1; j<=n; j++)            {                edge[index].u=i;                edge[index].v=j;                edge[index++].w=distance(i,j);            }        qsort(edge,index,sizeof(edge[0]),cmp);        creat();        m=-1;        for(i=1; i<n; i++)        {            int e=flag[i];            memset(visit,0,sizeof(visit));            visit[edge[e].u]=1;            ans=0;            dfs(edge[e].v);            max1=ans;            memset(visit,0,sizeof(visit));            visit[edge[e].v]=1;            ans=0;            dfs(edge[e].u);            max2=ans;            if(m<1.0*(max1+max2)/(sum-edge[e].w))                m=1.0*(max1+max2)/(sum-edge[e].w);        }        printf("%.2f\n",m);    }    return 0;}
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