[ZJOI2007] Hide and Seek (chain partition)

Portal

Stand idly by going to write it again with a chain of divide and conquer, the result is not good because Naogua Zi tune with the more than two hours. . .
In fact, the first time to play their own chain of divide and conquer

use $set$ maintains downward longest chain light son
the last path must be considered a one heavy chain (or a point) through

Let this path in this path statistics on the heavy chain
to maintain the longest chain up and down the chain and then stitching the longest, with the largest sub-segment and almost

#include<bits/stdc++.h>
#define cs const
#define pb push_back
using namespace std;
cs int N = 1e5 + 5; 
cs int INF = 1e9;
int fix(int x){ if(x-223206<-INF) x=-INF; return x;}
int read(){
	int cnt = 0, f = 1; char ch = 0;
	while(!isdigit(ch)){ ch = getchar(); if(ch == '-') f = -1; }
	while(isdigit(ch)) cnt = cnt*10 + (ch-'0'), ch = getchar();
	return cnt * f;
}
int n, m, ct, col[N];
vector<int> v[N];
int sz[N],son[N],dep[N],fa[N],top[N],bot[N],in[N],ps[N],sign;
multiset<int> S[N], Ans;
typedef multiset<int>::iterator It;
void pre_dfs(int u, int f){
	sz[u]=1;
	for(auto t:v[u]) if(t^f){
		dep[t]=dep[u]+1; fa[t]=u; 
		pre_dfs(t,u); sz[u] += sz[t];
		if(sz[t]>sz[son[u]]) son[u]=t;
	}
}
void dfs(int u, int tp){
	top[u]=tp; in[u]=++sign; ps[sign]=u; 
	if(son[u]) dfs(son[u],tp),bot[u]=bot[son[u]];
	else bot[u]=u, Ans.insert(-INF);
	for(auto t:v[u]) if((t^fa[u])&&(t^son[u])) dfs(t,t), S[u].insert(-INF);
}
struct data{ int lv,rv,mx,sm; };
data operator + (data a, data b){
	return (data){
		fix(max(a.lv,a.sm+b.lv)), fix(max(b.rv,b.sm+a.rv)),
		fix(max(max(a.mx,b.mx),a.rv+b.lv)), a.sm+b.sm
	};
}
namespace SGT{
	cs int N = ::N<<2;
	data t[N]; 
	#define mid ((l+r)>>1)
	void pushup(int x){ t[x]=t[x<<1]+t[x<<1|1]; }
	void build(int x, int l, int r){
		t[x].lv = t[x].rv = t[x].mx = -INF; t[x].sm = r-l+1;
		if(l == r) return; build(x<<1,l,mid); build(x<<1|1,mid+1,r);
	}
	void upt(int x, int l, int r, int p){
		if(l == r){
			t[x].lv = t[x].rv = t[x].mx = -INF;
			p = ps[p]; It it = S[p].end();
			if(S[p].size() >= 1) t[x].lv = t[x].rv = fix((*--it)+1);
			if(S[p].size() >= 2) t[x].mx = fix(t[x].lv + (*--it));
			return;
		} 
		if(p<=mid) upt(x<<1,l,mid,p);
		else upt(x<<1|1,mid+1,r,p); pushup(x);
	}
	data query(int x, int l, int r, int L, int R){
		if(L<=l && r<=R) return t[x]; 
		if(R<=mid) return query(x<<1,l,mid,L,R);
		else if(L>mid) return query(x<<1|1,mid+1,r,L,R);
		else return query(x<<1,l,mid,L,R)+query(x<<1|1,mid+1,r,L,R);
	}
}
void modify(int x, int op){
	bool FLAG = true; int vl = SGT::query(1,1,n,in[top[x]],in[bot[x]]).lv;
	while(x){
		int tp = fa[top[x]];
		if(tp){
			data nx = SGT::query(1,1,n,in[top[tp]],in[bot[tp]]);
			Ans.erase(Ans.find(nx.mx)); 
			S[tp].erase(S[tp].find(vl)); vl=nx.lv;
		}
		
		if(FLAG){
			Ans.erase(Ans.find(SGT::query(1,1,n,in[top[x]],in[bot[x]]).mx));
			if(op == 1) S[x].insert(0); 
			else S[x].erase(S[x].find(0));
			SGT::upt(1,1,n,in[x]); 
			Ans.insert(SGT::query(1,1,n,in[top[x]],in[bot[x]]).mx);
			FLAG = false;
		}
		
		if(tp){
			S[tp].insert(SGT::query(1,1,n,in[top[x]],in[bot[x]]).lv);
			SGT::upt(1,1,n,in[tp]); 
			Ans.insert(SGT::query(1,1,n,in[top[tp]],in[bot[tp]]).mx);
		} x = tp;
	}
}
int main(){
	n = ct = read();
	for(int i = 1; i < n; i++){
		int x = read(), y = read();
		v[x].pb(y); v[y].pb(x);
	} pre_dfs(1,0); dfs(1,1); SGT::build(1,1,n);
	for(int i = 1; i <= n; i++) modify(i,1);
	m = read();
	while(m--){
		char op[2]; scanf("%s", op);
		if(op[0] == 'G'){
			if(ct == 0) puts("-1");
			else if(ct == 1) puts("0");
			else cout << *(--Ans.end())-1 << '\n';
		}
		if(op[0] == 'C'){
			int x = read(); 
			if(col[x]==0) modify(x,-1); 
			else modify(x,1); col[x]^=1;
		}
	} return 0;
}