BZOJ 3306: 树

#include<bits/stdc++.h>
using namespace std;
const int N=100002,inf=1e9+7;
inline int read()
{
char ch=getchar(); int x=0,f=1;
while(ch<'0'||ch>'9'){if(ch=='-')f=-1; ch=getchar();}
while(ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+ch-'0'; ch=getchar();}
return x*f;
}
struct node{int y,next;}a
; int len,first
;
void ins(int x,int y){a[++len]=(node){y,first[x]},first[x]=len;}
int s
,e
,id,c
,mn[N<<2],f
[18],dep
,d[20];
void dfs(int x)
{
s[x]=++id;
for(int i=1;i<=17;i++)
if(f[x][i-1])f[x][i]=f[f[x][i-1]][i-1];
else break;
for(int k=first[x];k;k=a[k].next){
int y=a[k].y;
f[y][0]=x,dep[y]=dep[x]+1,dfs(y);
}
e[x]=id;
}
void change(int x,int l,int r,int k,int u)
{
if(l==r){mn[x]=u; return;}
int mid=(l+r)>>1,lc=x<<1,rc=lc|1;
if(k<=mid)change(lc,l,mid,k,u);
else change(rc,mid+1,r,k,u);
mn[x]=min(mn[lc],mn[rc]);
}
int query(int x,int l,int r,int ql,int qr)
{
if(ql>qr)return inf;
if(l==ql && r==qr)return mn[x];
int mid=(l+r)>>1,lc=x<<1,rc=lc|1;
if(ql>mid)return query(rc,mid+1,r,ql,qr);
else if(qr<=mid)return query(lc,l,mid,ql,qr);
return min(query(lc,l,mid,ql,mid),query(rc,mid+1,r,mid+1,qr));
}
int main()
{
int n=read(),m=read(),x,y,i;
d[0]=1; for(i=1;i<=17;i++)d[i]=d[i-1]<<1;
for(i=1;i<=n;i++)
{
x=read(),c[i]=read();
if(x)ins(x,i);
}
id=0; dfs(1);
for(i=1;i<=n;i++)change(1,1,n,s[i],c[i]);
int rt=1; char ch;
for(i=1;i<=m;i++)
{
scanf("\n%c",&ch);
if(ch=='V')x=read(),y=read(),change(1,1,n,s[x],y);
else if(ch=='E')rt=read();
else
{
x=read();
if(x==rt)printf("%d\n",mn[1]);
else if(s[x]<=s[rt] && e[x]>=e[rt])
{
y=rt; for(int j=17;j>=0;j--)if(dep[y]-dep[x]>d[j])y=f[y][j];
printf("%d\n",min(query(1,1,n,1,s[y]-1),query(1,1,n,e[y]+1,n)));
}
else printf("%d\n",query(1,1,n,s[x],e[x]));
}
}
return 0;
}