[BZOJ1050][HAOI2006]旅行comf 枚举+并查集

题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=1050

将边排序，枚举边权最小的边，依次加边直到S和T连通，更新答案。

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 int inline readint(){
     int Num;char ch;
     while((ch=getchar())<''||ch>'');Num=ch-'';
     while((ch=getchar())>=''&&ch<='') Num=Num*+ch-'';
     return Num;
 }
 int N,M,S,T;
 struct EDGE{
     int u,v,w;
     bool operator < (const EDGE &_)const{
         return w<_.w;
     }
 }edge[];
 int fa[];
 int inline Getfa(int x){
     return fa[x]==x?x:fa[x]=Getfa(fa[x]);
 }
 int inline Gcd(int a,int b){
     return !b?a:Gcd(b,a%b);
 }
 int main(){
     N=readint();
     M=readint();
     for(int i=;i<=M;i++){
         edge[i].u=readint();
         edge[i].v=readint();
         edge[i].w=readint();
     }
     sort(edge+,edge++M);
     S=readint();
     T=readint();
     int ansu=,ansd=;
     for(int i=;i<=M;i++){
         for(int j=;j<=N;j++) fa[j]=j;
         int mx;
         for(int j=i;j<=M;j++){
             int fx=Getfa(edge[j].u),
                 fy=Getfa(edge[j].v);
             if(fx==fy) continue;
             mx=edge[j].w;
             fa[fx]=fy;
             if(Getfa(S)==Getfa(T)) break;
         }
         if(Getfa(S)!=Getfa(T)) break;
         if(mx*ansd<ansu*edge[i].w){
             ansu=mx;
             ansd=edge[i].w;
         }
     }
     if(ansu==){
         puts("IMPOSSIBLE");
         return ;
     }
     int gcd=Gcd(ansu,ansd);
     ansu/=gcd;
     ansd/=gcd;
     if(ansd>) printf("%d/%d\n",ansu,ansd);
     else printf("%d\n",ansu);
     return ;
 }