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| #include<algorithm>
#include<iostream>
#include<iomanip>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<cstdio>
#include<cmath>
#include<queue>
using namespace std;
inline const int Get_Int() {
int num=0,bj=1;
char x=getchar();
while(x<'0'||x>'9') {
if(x=='-')bj=-1;
x=getchar();
}
while(x>='0'&&x<='9') {
num=num*10+x-'0';
x=getchar();
}
return num*bj;
}
int min(int a,int b) {
return a<b?a:b;
}
const int maxn=100005;
struct Tree {
int left,right,min;
Tree(int l=0,int r=0,int m=0x7fffffff/2):left(l),right(r),min(m) {}
};
struct Segment_Tree {
Tree tree[maxn*4];
#define ls index<<1
#define rs index<<1|1
void build(int index,int Left,int Right,int* a) {
tree[index]=Tree(Left,Right);
if(Left==Right) {
tree[index].min=a[Left];
return;
}
int mid=(Left+Right)>>1;
build(ls,Left,mid,a);
build(rs,mid+1,Right,a);
push_up(index);
}
void push_up(int index) {
tree[index].min=min(tree[ls].min,tree[rs].min);
}
void modify(int index,int target,int v) {
if(target>tree[index].right||target<tree[index].left)return;
if(tree[index].left==tree[index].right) {
tree[index].min=v;
return;
}
modify(ls,target,v);
modify(rs,target,v);
push_up(index);
}
int query(int index,int Left,int Right) {
if(Left>tree[index].right||Right<tree[index].left)return 0x7fffffff/2;
if(Left<=tree[index].left&&Right>=tree[index].right)return tree[index].min;
return min(query(ls,Left,Right),query(rs,Left,Right));
}
} st;
int n,q,step=0,root=1,a[maxn],b[maxn],p[maxn][25],First[maxn],Last[maxn],Depth[maxn];
vector<int>edges[maxn];
void AddEdge(int x,int y) {
edges[x].push_back(y);
}
void Dfs(int Now,int fa,int depth) {
First[Now]=++step;
b[step]=a[Now];
Depth[Now]=depth;
p[Now][0]=fa;
for(int j=1; j<=log2(n); j++)
if(~p[Now][j-1])p[Now][j]=p[p[Now][j-1]][j-1];
for(int Next:edges[Now])Dfs(Next,Now,depth+1);
Last[Now]=step;
}
int LCA(int x,int y,int& pos) {
if(Depth[x]<Depth[y])swap(x,y);
int k=log2(Depth[x]);
for(int i=k; i>=0; i--)
if(Depth[x]-(1<<i)>Depth[y])x=p[x][i];
if(p[x][0]==y) {
pos=x;
return y;
}
for(int i=k; i>=0; i--)
if(~p[x][i]&&p[x][i]!=p[y][i]) {
x=p[x][i];
y=p[y][i];
}
return p[x][0];
}
int main() {
memset(p,-1,sizeof(p));
n=Get_Int();
q=Get_Int();
for(int i=1; i<=n; i++) {
int f=Get_Int(),x=Get_Int();
if(f)AddEdge(f,i);
a[i]=x;
}
Dfs(1,-1,1);
st.build(1,1,n,b);
for(int i=1; i<=q; i++) {
char opt=' ';
while(!isalpha(opt))opt=getchar();
if(opt=='V') {
int x=Get_Int(),y=Get_Int();
st.modify(1,First[x],y);
} else if(opt=='E')root=Get_Int();
else {
int x=Get_Int(),pos=0;
if(x==root) {
printf("%d\n",st.tree[1].min);
continue;
}
int lca=LCA(x,root,pos);
if(lca!=x)printf("%d\n",st.query(1,First[x],Last[x]));
else printf("%d\n",min(st.query(1,1,First[pos]-1),st.query(1,Last[pos]+1,n)));
}
}
return 0;
}
|
