记录编号	397271	评测结果	AAAAA
题目名称	2281.[HZOI 2015]白黑树	最终得分	100
用户昵称	AntiLeaf	是否通过	通过
代码语言	C++	运行时间	0.261 s
提交时间	2017-04-19 21:38:40	内存使用	7.37 MiB

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
const int maxn=200010;
void dfs1(int);
void dfs2(int);
int LCA(int,int);
template<typename cmp>struct binary_heap{
	priority_queue<int,vector<int>,cmp>q1,q2;
	void push(int x){q1.push(x);}
	void erase(int x){q2.push(x);}
	int top(){
		while(!q2.empty()&&q1.top()==q2.top()){
			q1.pop();
			q2.pop();
		}
		return q1.top();
	}
	bool empty(){
		while(!q2.empty()&&q1.top()==q2.top()){
			q1.pop();
			q2.pop();
		}
		return q1.empty();
	}
};
vector<int>G[maxn];
int p[maxn],d[maxn],dfn[maxn],tim=0;
int size[maxn],son[maxn],top[maxn];
struct cmp1{cmp1(){}bool operator()(int x,int y){return dfn[x]<dfn[y];}};
binary_heap<cmp1>heap1;
struct cmp2{cmp2(){}bool operator()(int x,int y){return dfn[x]>dfn[y];}};
binary_heap<cmp2>heap2;
bool col[maxn]={false};
char c;
int n,m,x,y;
int main(){
	freopen("C_Tree.in","r",stdin);
	freopen("C_Tree.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i=1;i<n;i++){
		scanf("%d%d",&x,&y);
		G[x].push_back(y);
		G[y].push_back(x);
	}
	dfs1(1);
	dfs2(1);
	while(m--){
		scanf(" %c%d",&c,&x);
		if(c=='M'){
			if(col[x]){
				heap1.erase(x);
				heap2.erase(x);
			}
			else{
				heap1.push(x);
				heap2.push(x);
			}
			col[x]^=true;
		}
		else{
			if(heap1.empty())printf("-1\n");
			else{
				int u=LCA(x,heap1.top()),v=LCA(x,heap2.top());
				printf("%d\n",d[u]<d[v]?u:v);
			}
		}
	}
	return 0;
}
void dfs1(int x){
	dfn[x]=++tim;
	size[x]=1;
	d[x]=d[p[x]]+1;
	for(int i=0;i<(int)G[x].size();i++)if(G[x][i]!=p[x]){
		p[G[x][i]]=x;
		dfs1(G[x][i]);
		size[x]+=size[G[x][i]];
		if(size[G[x][i]]>size[son[x]])son[x]=G[x][i];
	}
}
void dfs2(int x){
	if(x==son[p[x]])top[x]=top[p[x]];
	else top[x]=x;
	for(int i=0;i<(int)G[x].size();i++)if(G[x][i]!=p[x])dfs2(G[x][i]);
}
int LCA(int x,int y){
	while(top[x]!=top[y]){
		if(d[top[x]]<d[top[y]])swap(x,y);
		x=p[top[x]];
	}
	return d[x]<d[y]?x:y;
}