poj (简单题:kruskal判断最小生成树是否唯一--求次小生成树 )

#include<iostream>#include<cstdio>#include<cstring>#include<set>#include<cstdio>#include<string>#include<map>#include<algorithm>using namespace std;const int inf=999999;const int maxn=10000;int n,m;struct EDGE{    int u,v,len;    int vis;}edge[maxn*100];int fa[maxn];int vv[maxn];bool cmp(EDGE a,EDGE b){    return a.len<b.len;}int findx(int a){    if(fa[a]==a)    return a;    else    return findx(fa[a]);}void init(){    for(int i=0;i<=n;i++)    {        fa[i]=i;    }}void Union(int a,int b){    int aa=findx(a);    int bb=findx(b);    if(aa<bb)    fa[bb]=aa;    else    fa[aa]=bb;}int kruskal(){    int k=0;    init();    int sum=0;    for(int i=0;i<m;i++)    {        int aa=edge[i].u;        int bb=edge[i].v;        if(findx(aa)!=findx(bb))        {            k++;            edge[i].vis=1;            sum+=edge[i].len;            Union(aa,bb);        }    }    if(k<n-1)    return 0;    else    return sum;}int MMST(){    init();    int sum=0;    int k=0;    for(int i=0;i<m;i++)    {       if(!vv[i])       {            int aa=edge[i].u;            int bb=edge[i].v;           if(findx(aa)!=findx(bb))           {            k++;            sum+=edge[i].len;            Union(aa,bb);           }       }    }    if(k<n-1)    return inf;    else return sum;}int main(){    int cas;    cin>>cas;   while(cas--)   {       cin>>n>>m;     memset(vv,0,sizeof(vv));    for(int i=0;i<m;i++)    {        cin>>edge[i].u>>edge[i].v>>edge[i].len;        edge[i].vis=0;    }    sort(edge,edge+m,cmp);    int sum=kruskal();    int ans=inf;    for(int i=0;i<m;i++)    {        if(edge[i].vis)        {            vv[i]=1;            int tmp=MMST();            ans=min(ans,tmp);            vv[i]=0;        }    }    if(ans==sum)    cout<<"Not Unique!" <<endl;    else    cout<<sum<<endl;   }    return 0;}