题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1095
这道题可以用动态树分治水过去，但是代码量相当大，于是乎我偷懒用了括号序列的写法，好不容易A掉了额。（神奇的传送门：http://www.shuizilong.com/house/archives/bzoj-1095-zjoi2007hide-%E6%8D%89%E8%BF%B7%E8%97%8F/）
代码：
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <vector>
#include <cmath>
using namespace std ;
#define AddEdge( s , t ) Add( s , t ),Add( t , s )
#define Add( s , t ) E[ s ].push_back( t )
#define left( t ) ( t <<1)
#define right( t ) (left( t )^1)
#define L( t ) Left[ t ]
#define R( t ) Right[ t ]
#define LP( t ) left_push[ t ]
#define RP( t ) right_push[ t ]
#define LM( t ) left_minus[ t ]
#define RM( t ) right_minus[ t ]
#define D( t ) Dist[ t ]
#define A( t ) la[ t ]
#define B( t ) rb[ t ]
#define rep( i , x ) for(int i =0; i ++< x ;)
#define travel( x ) for( vector <int>:: iterator p = E[ x ].begin( ); p != E[ x ].end( );++ p )
const int maxn =101000;
const int inf =1000000000;
const int maxv = maxn <<3;
vector <int> E[ maxn ];
int n , m , in[ maxn ], out[ maxn ], dfn[ maxn <<1], num[ maxn <<1], Index =0;
bool col[ maxn <<1];
void dfs(int v ,int u ){
num[ in[ v ]=++ Index ]=0;
travel( v )if(*p != u )dfs(*p , v );
num[ out[ v ]=++ Index ]=1;
}
int left_push[ maxv ], right_push[ maxv ], left_minus[ maxv ], right_minus[ maxv ];
int Left[ maxv ], Right[ maxv ], Dist[ maxv ], la[ maxv ], rb[ maxv ];
void update(int t ){
if(L( t )<R( t )){
if(B(left( t ))>A(right( t ))){
A( t )=A(left( t ));
B( t )=B(right( t ))+B(left( t ))-A(right( t ));
}else{
A( t )=A(left( t ))+A(right( t ))-B(left( t ));
B( t )=B(right( t ));
}
LP( t )=max(LP(left( t )),max(A(left( t ))-B(left( t ))+LP(right( t )),A(left( t ))+B(left( t ))+LM(right( t ))));
LM( t )=max(LM(left( t )),B(left( t ))-A(left( t ))+LM(right( t )));
RP( t )=max(RP(right( t )),max(A(right( t ))+B(right( t ))+RM(left( t )),B(right( t ))-A(right( t ))+RP(left( t ))));
RM( t )=max(RM(right( t )),A(right( t ))-B(right( t ))+RM(left( t )));
D( t )=max(max(D(left( t )),D(right( t ))),max(RM(left( t ))+LP(right( t )),RP(left( t ))+LM(right( t ))));
}
}
void build(int l ,int r ,int t ){
L( t )= l ,R( t )= r ;
if( l == r ){
A( t )= num[ l ]==1?1:0;
B( t )= num[ l ]==0?1:0;
if(! col[ r +1]){
LP( t )=A( t )+B( t );
LM( t )=B( t )-A( t );
}else{
LP( t )=LM( t )=- inf ;
}
if(! col[ l -1]){
RP( t )=A( t )+B( t );
RM( t )=A( t )-B( t );
}else{
RP( t )=RM( t )=- inf ;
}
if(! col[ l -1]&&! col[ r +1]){
D( t )=1;
}else D( t )=- inf ;
return;
}
int mid =( l + r )>>1;
build( l , mid ,left( t )),build( mid +1, r ,right( t ));
update( t );
}
void change(int x ,int t ){
if(L( t )==R( t )){
if(! col[ x +1]){
LP( t )=A( t )+B( t );
LM( t )=B( t )-A( t );
}else{
LP( t )=LM( t )=- inf ;
}
if(! col[ x -1]){
RP( t )=A( t )+B( t );
RM( t )=A( t )-B( t );
}else{
RP( t )=RM( t )=- inf ;
}
if(! col[ x -1]&&! col[ x +1]){
D( t )=1;
}else D( t )=- inf ;
return;
}
int mid =(L( t )+R( t ))>>1;
change( x , x <= mid ?left( t ):right( t ));
update( t );
}
void Change(int v ){
col[ in[ v ]]^=true;
if( in[ v ]-1)change( in[ v ]-1,1);
if( in[ v ]<( n <<1))change( in[ v ]+1,1);
col[ out[ v ]]^=true;
if( out[ v ]-1)change( out[ v ]-1,1);
if( out[ v ]<( n <<1))change( out[ v ]+1,1);
}
int main( ){
scanf("%d",&n );
rep( i , n -1){
int s , t ;scanf("%d%d",&s ,&t );
AddEdge( s , t );
}
dfs(1,0);
memset( col ,false,sizeof( col ));
col[0]= col[( n <<1)+1]=true;
build(1, n <<1,1);
scanf("%d",&m );
while( m --){
int ch ;for( ch =getchar( ); ch !='G'&& ch !='C'; ch =getchar( ));
if( ch =='C'){
int v ;scanf("%d",&v );
Change( v );
}else printf("%d\n",D(1));
}
return 0;
}
