YYH的营救计划

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int read(){
    int t=1,num=0;char c=getchar();
    while(c>'9'||c<'0'){if(c=='-')t=-1;c=getchar();}
    while(c>='0'&&c<='9'){num=num*10+c-'0';c=getchar();}
    return num*t;
}
const int maxm=400100;
struct edge{int f,t,c;}g[maxm];
bool cmp(edge x,edge y){return x.c<y.c;}
int fa[maxm],n,m,s,t;
int find(int x){
    if(fa[x]==x)return x;
    return fa[x]=find(fa[x]);
}
void unite(int x,int y){
    int fx=find(x),fy=find(y);
    if(fx==fy)return;
    fa[fx]=fy;
}
int kru(){
    sort(g+1,g+m+1,cmp);
    for(int i=1;i<=n;i++)fa[i]=i;
    for(int i=1;i<=m;i++){
        edge x=g[i];
        if(find(x.f)!=find(x.t)){
            unite(x.f,x.t);
            if(find(s)==find(t))return g[i].c;
        }
    }
}
int main()
{
    n=read();m=read();s=read();t=read();
    for(int i=1;i<=m;i++){
        int x,y,z;
        x=read();y=read();z=read();
        g[i]=(edge){x,y,z};
    }
    cout<<kru();
    return 0;
}

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