打完了，发现你 AC 了，没得玩了
贴一个我的树剖模板
```cpp
#include<bits/stdc++.h>
using namespace std;typedef int I;const I inf=1073741824;typedef long long LL;I FL,CH;template<typename T>bool in(T&a){for(FL=1;!isdigit(CH)&&CH!=EOF;CH=getchar())if(CH=='-')FL=-1;for(a=0;isdigit(CH);CH=getchar())a=a*10+CH-'0';return a*=FL,CH==EOF?0:1;}template<typename T,typename...Args>I in(T&a,Args&...args){return in(a)+in(args...);}
const I N=1e5+10;
I ey[N<<1],nx[N<<1],hd[N],ec=1,n;
I siz[N],dfn[N],fa[N],d[N],frt[N<<1],fri[N],tp[N<<1],hs[N],clk,idf[N],ez[N<<1],a[N];
void conn(I x,I y,I z){
ey[++ec]=y;nx[ec]=hd[x];hd[x]=ec;
ez[ec]=z;
}void dfs1(I x){
siz[x]=1;
d[x]=d[fa[x]]+1;
for(I i=hd[x],y;i;i=nx[i]){
y=ey[i];
if(y==fa[x])
continue;
fa[y]=x;
frt[i]=frt[i^1]=y;
fri[y]=i;
a[y]=ez[i];
dfs1(y);
siz[x]+=siz[y];
if(siz[y]>siz[hs[x]]){
hs[x]=y;
}
}
}void dfs2(I x,I tp){
dfn[x]=++clk;
idf[clk]=x;
::tp[x]=tp;
if(hs[x]){
dfs2(hs[x],tp);
}for(I i=hd[x],y;i;i=nx[i]){
y=ey[i];
if(y==fa[x]||y==hs[x])continue;
dfs2(y,y);
}
}
I M[N<<1],L[N<<1],R[N<<1],cnt;
void psu(I x){
M[x]=max(M[L[x]],M[R[x]]);
}
void build(I&p,I l,I r){
if(!p)p=++cnt;
if(l==r){
M[p]=a[idf[l]];
return;
}I mid=l+r>>1;
build(L[p],l,mid);
build(R[p],mid+1,r);
psu(p);
}
I cp,cx,rt;
void chg(I p,I l,I r){
if(l==r){
M[p]=cx;
return;
}I mid=l+r>>1;
if(cp<=mid)chg(L[p],l,mid);
if(mid<cp)chg(R[p],mid+1,r);
psu(p);
}
I ql,qr;
I qry(I p,I l,I r){
if(ql<=l&&r<=qr)return M[p];
I mid=l+r>>1;
if(qr<=mid)return qry(L[p],l,mid);
if(ql>mid)return qry(R[p],mid+1,r);
return max(qry(L[p],l,mid),qry(R[p],mid+1,r));
}
I Qry(I l,I r){
ql=l;qr=r;
return qry(rt,1,n);
}
void pcss_chgedge(I id,I w){
cp=dfn[frt[id]];
cx=w;
chg(rt,1,n);
}
void chgsingle(I x,I w){
cp=dfn[x];
cx=w;
chg(rt,1,n);
}
I LCA(I x,I y){
while(tp[x]^tp[y]){
if(d[tp[x]]<d[tp[y]])x^=y^=x^=y;
x=fa[tp[x]];
}return d[x]>d[y]?y:x;
}
I qry_path(I x,I y){
if(x==y)return 0;
I lc=LCA(x,y),lcax=Qry(dfn[lc],dfn[lc]),ans=-inf;
chgsingle(lc,-inf);
while(tp[x]^tp[y]){
if(d[tp[x]]<d[tp[y]])swap(x,y);
ans=max(ans,Qry(dfn[tp[x]],dfn[x]));
x=fa[tp[x]];
}if(d[x]>d[y])swap(x,y);
ans=max(ans,Qry(dfn[x],dfn[y]));
chgsingle(lc,lcax);
return ans;
}
char ops[10];
int main(){
a[1]=-inf;
in(n);
for(I i=1,x,y,z;i<n;++i){
in(x,y,z);
conn(x,y,z);
conn(y,x,z);
}
dfs1(1);
dfs2(1,1);
// printf("finished df2\n");
build(rt,1,n);
I x,t;
while(1){
while(!isalpha(CH))CH=getchar();
if(CH=='D')break;
if(CH=='C'){
in(x,t);
pcss_chgedge(x<<1,t);
}else{
in(x,t);
printf("%d\n",qry_path(x,t));
}
}
return 0;
}
```
by CrTsIr400 @ 2023-01-13 21:16:42
这个码量不大，理解各变量的作用就好了，
by CrTsIr400 @ 2023-01-13 21:17:12
@[SmallTualatin](/user/121995) 好的，谢谢
by DengDuck @ 2023-01-13 21:18:14