http://www.lydsy.com/JudgeOnline/problem.php?id=1095
好像有2种做法：线段树维护括号编码&动态树分治。
线段树维护括号编码：
这篇论文是讲得极好的。
#include<cstdio> #include<cstdlib> #include<iostream> #include<fstream> #include<algorithm> #include<cstring> #include<string> #include<cmath> #include<queue> #include<stack> #include<map> #include<utility> #include<set> #include<bitset> #include<vector> #include<functional> #include<deque> #include<cctype> #include<climits> #include<complex> //#include<bits/stdc++.h>适用于CF,UOJ，但不适用于poj using namespace std; typedef long long LL; typedef double DB; typedef pair<int,int> PII; typedef complex<DB> CP; #define mmst(a,v) memset(a,v,sizeof(a)) #define mmcy(a,b) memcpy(a,b,sizeof(a)) #define fill(a,l,r,v) fill(a+l,a+r+1,v) #define re(i,a,b) for(i=(a);i<=(b);i++) #define red(i,a,b) for(i=(a);i>=(b);i--) #define ire(i,x) for(typedef(x.begin()) i=x.begin();i!=x.end();i++) #define fi first #define se second #define m_p(a,b) make_pair(a,b) #define p_b(a) push_back(a) #define SF scanf #define PF printf #define two(k) (1<<(k)) template<class T>inline T sqr(T x){return x*x;} template<class T>inline void upmin(T &t,T tmp){if(t>tmp)t=tmp;} template<class T>inline void upmax(T &t,T tmp){if(t<tmp)t=tmp;} inline int sgn(DB x){if(abs(x)<1e-9)return 0;return(x>0)?1:-1;} const DB Pi=acos(-1.0); int gint() { int res=0;bool neg=0;char z; for(z=getchar();z!=EOF && z!='-' && !isdigit(z);z=getchar()); if(z==EOF)return 0; if(z=='-'){neg=1;z=getchar();} for(;z!=EOF && isdigit(z);res=res*10+z-'0',z=getchar()); return (neg)?-res:res; } LL gll() { LL res=0;bool neg=0;char z; for(z=getchar();z!=EOF && z!='-' && !isdigit(z);z=getchar()); if(z==EOF)return 0; if(z=='-'){neg=1;z=getchar();} for(;z!=EOF && isdigit(z);res=res*10+z-'0',z=getchar()); return (neg)?-res:res; } const int maxn=100000; int n; int now,info[maxn+100]; struct Tedge{int v,next;}edge[2*maxn+100]; int status[maxn+100],ge; void addedge(int u,int v){now++;edge[now].v=v;edge[now].next=info[u];info[u]=now;} int cnt,ty[3*maxn+100],pos[maxn+100]; void dfs(int u) { ty[++cnt]=-1; ty[++cnt]=u; pos[u]=cnt; int i,v; for(i=info[u],v=edge[i].v;i!=-1;i=edge[i].next,v=edge[i].v)if(!pos[v])dfs(v); ty[++cnt]=-2; } struct Tdata { int a,b; Tdata(int _a=0,int _b=0){a=_a;b=_b;} friend Tdata operator +(Tdata l,Tdata r){return (l.b<=r.a)?Tdata(l.a+r.a-l.b,r.b):Tdata(l.a,l.b-r.a+r.b);} friend bool operator ==(Tdata x,Tdata y){return x.a==y.a && x.b==y.b;} friend bool operator !=(Tdata x,Tdata y){return !(x==y);} }; Tdata null=Tdata(-1,-1); /* dist 子区间的最大值 whole 区间[l,r]的二元组(a,b) lp 右端点为黑点的a+b最大的前缀的二元组(a,b) rp 左端点为黑点的a+b最大的后缀的二元组(a,b) lm 右端点为黑点的b-a最大的前缀的二元组(a,b) rm 左端点为黑点的a-b最大的后缀的二元组(a,b) null表示不存在 */ struct Tnode { int dist; Tdata whole,lp,rp,lm,rm; void init(int x); }; void Tnode::init(int x) { int lcnt=(ty[x]==-2),rcnt=(ty[x]==-1); whole=Tdata(lcnt,rcnt); dist=-1; if(ty[x]>=1 && status[ty[x]]) lp=rp=lm=rm=whole; else lp=rp=lm=rm=null; } Tnode make_up(Tnode x,Tnode y) { Tnode res;Tdata p; res.whole=x.whole+y.whole; res.lp=x.lp; if(y.lp!=null) { p=x.whole+y.lp; if(res.lp==null || res.lp.a+res.lp.b<p.a+p.b)res.lp=p; } if(y.lm!=null) { p=x.whole+y.lm; if(res.lp==null || res.lp.a+res.lp.b<p.a+p.b)res.lp=p; } res.rp=y.rp; if(x.rp!=null) { p=x.rp+y.whole; if(res.rp==null || res.rp.a+res.rp.b<p.a+p.b)res.rp=p; } if(x.rm!=null) { p=x.rm+y.whole; if(res.rp==null || res.rp.a+res.rp.b<p.a+p.b)res.rp=p; } res.lm=x.lm; if(y.lm!=null) { p=x.whole+y.lm; if(res.lm==null || res.lm.b-res.lm.a<p.b-p.a)res.lm=p; } res.rm=y.rm; if(x.rm!=null) { p=x.rm+y.whole; if(res.rm==null || res.rm.a-res.rm.b<p.a-p.b)res.rm=p; } res.dist=max(x.dist,y.dist); if(x.rp!=null && y.lm!=null) { p=x.rp+y.lm; upmax(res.dist,p.a+p.b); } if(x.rm!=null && y.lp!=null) { p=x.rm+y.lp; upmax(res.dist,p.a+p.b); } return res; } Tnode tr[4*3*maxn+100]; void build(int rt,int l,int r) { if(l==r){tr[rt].init(l);return;} int mid=(l+r)>>1; build(rt<<1,l,mid); build(rt<<1|1,mid+1,r); tr[rt]=make_up(tr[rt<<1],tr[rt<<1|1]); } void update(int rt,int l,int r,int x) { if(l==r){tr[rt].init(l);return;} int mid=(l+r)/2; if(x<=mid)update(rt<<1,l,mid,x);else update(rt<<1|1,mid+1,r,x); tr[rt]=make_up(tr[rt<<1],tr[rt<<1|1]); } int main() { freopen("bzoj1095.in","r",stdin); freopen("bzoj1095.out","w",stdout); int i; n=gint(); now=-1;mmst(info,-1); re(i,1,n-1){int u=gint(),v=gint();addedge(u,v);addedge(v,u);} dfs(1); re(i,1,n)status[i]=1;ge=n; build(1,1,cnt); int Q;SF("%d\n",&Q); while(Q--) { char t;SF("%c",&t); if(t=='G') { if(ge==0)PF("-1\n");else if(ge==1) PF("0\n"); else PF("%d\n",tr[1].dist); } else { int x;SF("%d",&x); status[x]^=1; if(status[x])ge++;else ge--; update(1,1,cnt,pos[x]); } SF("\n"); } return 0; }