BZOJ 4551 [Tjoi2016&Heoi2016]树

题解：动态树，维护Splay最深的被标记过的点

每个询问先Access(x);

当然用树链剖分也可以

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#include<iostream> #include<cstdio> #include<cstring> #include<queue> using namespace std; const int maxn=100009; const int oo=1000000000;   int n,T;   int fa[maxn],ch[maxn][2],dest[maxn],v[maxn]; inline int son(int x){     if(ch[fa[x]][1]==x)return 1;     else return 0; } inline void pushup(int x){     dest[x]=dest[ch[x][1]];     if(!dest[x]){         if(v[x])dest[x]=x;     }     if(!dest[x])dest[x]=dest[ch[x][0]]; } inline bool isroot(int x){     return (ch[fa[x]][0]!=x)&&(ch[fa[x]][1]!=x); }   inline void Rotate(int x){     int y=fa[x];     int z=fa[y];     int b=son(x),c=son(y);     int a=ch[x][b^1];     if(!isroot(y))ch[z][c]=x;     fa[x]=z;     if(a)fa[a]=y;     ch[y][b]=a;     fa[y]=x;ch[x][b^1]=y;     pushup(y);pushup(x); } void Splay(int x){     while(!isroot(x)){         int y=fa[x];         if(isroot(y)){             Rotate(x);         }else{             if(son(x)==son(y)){                 Rotate(y);Rotate(x);             }else{                 Rotate(x);Rotate(x);             }         }     } }   void Access(int x){     for(int t=0;x;t=x,x=fa[x]){         Splay(x);ch[x][1]=t;pushup(x);     } }     int cntedge; int head[maxn]; int to[maxn<<1],nex[maxn<<1]; void Addedge(int x,int y){      nex[++cntedge]=head[x];      to[cntedge]=y;      head[x]=cntedge; }   queue<int>q; int father[maxn]; void Bfs(){     q.push(1);     while(!q.empty()){         int x=q.front();q.pop();         for(int i=head[x];i;i=nex[i]){             if(to[i]==father[x])continue;             father[to[i]]=x;             fa[to[i]]=x;             q.push(to[i]);         }     } }   int main(){     scanf("%d%d",&n,&T);     for(int i=1;i<=n-1;++i){         int x,y;         scanf("%d%d",&x,&y);         Addedge(x,y);         Addedge(y,x);     }           v[1]=1;dest[1]=1;     Bfs();     while(T--){         char opty[10];         scanf("%s",opty);         int x;         scanf("%d",&x);         if(opty[0]=='C'){             Splay(x);v[x]=1;pushup(x);         }else{             Access(x);Splay(x);printf("%d\n",dest[x]);         }     }     return 0; }