就是用 lct 維護最小生成樹
ref

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
using namespace std;
typedef pair<int,int> par;
int n, m, q, val[200005], zdz[200005], ans[200005], ch[200005][2];
int fa[200005];
bool vis[100005], rev[200005];
map<par,int> mp;
struct Edge{
    int
 
 fro, too, val;
}edge[100005];
struct Ques{
    int opt, x, y;
}qu[100005];
bool cmp(Edge x, Edge y){
    return x.val<y.val;
}
bool isRoot(int x){
    return ch[fa[x]][0]!=x && ch[fa[x]][1]!=x;
}
int getW(int x){
    return ch[fa[x]][1]==x;
}
void upd(int x){
    zdz[x] = val[x];
    if(edge[zdz[ch[x][0
 
]]].val>edge[zdz[x]].val)
        zdz[x] = zdz[ch[x][0]];
    if(edge[zdz[ch[x][1]]].val>edge[zdz[x]].val)
        zdz[x] = zdz[ch[x][1]];
}
void pushDown(int x){
    if(rev[x]){
        swap(ch[x][0], ch[x][1]);
        rev[ch[x][0]] ^= 1;
        rev[ch[x][1]] ^= 1;
        rev[x] = false;
    }
}
void
 
 xf(int x){
    if(fa[x])   xf(fa[x]);
    pushDown(x);
}
void rotate(int x){
    int old=fa[x], oldf=fa[old], w=getW(x);
    if(!isRoot(old))    ch[oldf][ch[oldf][1]==old] = x;
    ch[old][w] = ch[x][w^1]; ch[x][w^1] = old;
    fa[ch[old][w]] = old; fa[ch[x][w^1]] = x; fa[x] = oldf;
    upd(old); upd(x);
}
void splay(int x){
    xf(x);
    while(!isRoot(x)){
        int f=fa[x];
        if(!isRoot(f))
            rotate(getW(x)==getW(f)?f:x);
        rotate(x);
    }
    upd(x);
}
void access(int x){
    int y=0;
    while(x){
        splay(x);
        ch[x][1] = y;
        upd(x);
        y = x;
        x = fa[x];
    }
}
int findroot(int x){
    access(x);
    splay(x);
    while(ch[x][0])
        x = ch[x][0];
    splay(x);
    return x;
}
void makeroot(int x){
    access(x);
    splay(x);
    rev[x] ^= 1;
}
void split(int x, int y){
    makeroot(x);
    access(y);
    splay(y);
}
void link(int x, int y){
    makeroot(x);
    fa[x] = y;
}
void cut(int x, int y){
    split(x, y);
    fa[x] = ch[y][0] = 0;
}
int main(){//anonymous Pro Regular
    cin>>n>>m>>q;
    for(int i=1; i<=m; i++){
        scanf("%d %d %d", &edge[i].fro, &edge[i].too, &edge[i].val);
        if(edge[i].fro>edge[i].too) swap(edge[i].fro, edge[i].too);
    }
    sort(edge+1, edge+1+m, cmp);
    for(int i=1; i<=m; i++)
        mp[make_pair(edge[i].fro, edge[i].too)] = i;
    for(int i=1; i<=q; i++){
        scanf("%d %d %d", &qu[i].opt, &qu[i].x, &qu[i].y);
        if(qu[i].x>qu[i].y) swap(qu[i].x, qu[i].y);
        if(qu[i].opt==2)
            vis[mp[make_pair(qu[i].x, qu[i].y)]] = true;
    }
    for(int i=n+1; i<=n+m; i++)
        val[i] = zdz[i] = i - n;
    int tmpcnt=0;
    for(int i=1; i<=m; i++){
        if(tmpcnt==n-1) break;
        if(vis[i] || findroot(edge[i].fro)==findroot(edge[i].too))  continue;
        link(edge[i].fro, i+n); link(edge[i].too, i+n);
        tmpcnt++;
    }
    for(int i=q; i; i--){
        if(qu[i].opt==1){
            split(qu[i].x, qu[i].y);
            ans[i] = edge[zdz[qu[i].y]].val;
        }
        else{
            split(qu[i].x, qu[i].y);
            int idx=mp[make_pair(qu[i].x, qu[i].y)];
            int tmp=zdz[qu[i].y];
            if(edge[idx].val<edge[tmp].val){
                cut(edge[tmp].fro, tmp+n);
                cut(edge[tmp].too, tmp+n);
                link(edge[idx].fro, idx+n);
                link(edge[idx].too, idx+n);
            }
        }
    }
    for(int i=1; i<=q; i++)
        if(qu[i].opt==1)
            printf("%d\n", ans[i]);
    return 0;
}

luogu4172 [WC2006]水管局長