https://blog.csdn.net/tenkuo/article/details/153771297

#include<bits/stdc++.h>
using namespace std;
const int N=510;
const int M=5100;
struct edge{int x,y,w,pre;}a[M*2];int alen,last[N];
void add(int x,int y,int w){alen++;a[alen]=edge{x,y,w,last[x]};last[x]=alen;}
int n,m,fa[N];
int findfa(int x){return fa[x]==x? x : fa[x]=findfa(fa[x]);}
bool cmp(edge &a,edge &b){return a.w>b.w;}
int main()
{
    int n,m;scanf("%d%d",&n,&m);
    alen=0;memset(last,0,sizeof(last));
    for(int i=1;i<=n;i++) fa[i]=i;
    for(int i=1,x,y,w;i<=m;i++)
    {
        scanf("%d%d%d",&x,&y,&w);
        add(x,y,w);
        fa[findfa(x)]=findfa(y);
    } 
    int st,ed;scanf("%d%d",&st,&ed);
    if(findfa(st)!=findfa(ed)){puts("IMPOSSIBLE");return 0;}
    sort(a+1,a+1+alen,cmp);
    double ans=1e10;
    int mx,mi;
    for(int i=1;i<=m;i++)
    {
        for(int k=1;k<=n;k++) fa[k]=k;
        
        for(int j=i;j<=m;j++)
        {
            int x=a[j].x,y=a[j].y;
            fa[findfa(x)]=findfa(y);
            if(findfa(st)==findfa(ed))
            {
                double tmp=(1.0*a[i].w)/(1.0*a[j].w);
                if(tmp<ans) mx=a[i].w,mi=a[j].w,ans=tmp;
                break;
            }
        }
    } 
    if(mx/mi*mi==mx)printf("%d\n",mx/mi);
    else printf("%d/%d\n",mx/__gcd(mx,mi),mi/__gcd(mx,mi));
    return 0;
}