BZOJ4551 [Tjoi2016&Heoi2016]树

TJOI居然考这么傻逼的题……根JLOI一比真是天壤之别-_-

转成dfs序，然后相当于区间以deep为关键字去max，直接线段树维护就好

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<ctime>
#include<algorithm>
#include<iomanip>
#include<vector>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<bitset>
using namespace std;
#define MAXN 100010
#define MAXM 1010
#define ll long long
#define INF 1000000000
#define MOD 1000000007
#define eps 1e-8
struct vec{
int to;
int fro;
};
vec mp[MAXN];
int tai[MAXN],cnt;
int ch[MAXN*4];
int dep[MAXN];
int dfn[MAXN],siz[MAXN],tim;
int n,m;
inline void be(int x,int y){
mp[++cnt].to=y;
mp[cnt].fro=tai[x];
tai[x]=cnt;
}
void dfs(int x){
int i,y;
siz[x]=1;
dfn[x]=++tim;
for(i=tai[x];i;i=mp[i].fro){
y=mp[i].to;
if(!siz[y]){
dep[y]=dep[x]+1;
dfs(y);
siz[x]+=siz[y];
}
}
}
inline void toch(int x,int y){
if(dep[y]>dep[ch[x]]){
ch[x]=y;
}
}
inline void pd(int x){
if(ch[x]){
toch(x<<1,ch[x]);
toch(x<<1|1,ch[x]);
ch[x]=0;
}
}
void change(int x,int y,int z,int l,int r,int cv){
if(y==l&&z==r){
toch(x,cv);
return ;
}
pd(x);
int mid=y+z>>1;
if(r<=mid){
change(x<<1,y,mid,l,r,cv);
}else if(l>mid){
change(x<<1|1,mid+1,z,l,r,cv);
}else{
change(x<<1,y,mid,l,mid,cv);
change(x<<1|1,mid+1,z,mid+1,r,cv);
}
}
int ask(int x,int y,int z,int p){
if(y==z){
return ch[x];
}
pd(x);
int mid=y+z>>1;
if(p<=mid){
return ask(x<<1,y,mid,p);
}else{
return ask(x<<1|1,mid+1,z,p);
}
}
int main(){
int i,x,y;
char o[2];
scanf("%d%d",&n,&m);
for(i=1;i<n;i++){
scanf("%d%d",&x,&y);
be(x,y);
}
dep[1]=1;
dfs(1);
change(1,1,n,1,n,1);
for(i=1;i<=m;i++){
scanf("%s%d",o,&x);
if(o[0]=='Q'){
printf("%d\n",ask(1,1,n,dfn[x]));
}else{
change(1,1,n,dfn[x],dfn[x]+siz[x]-1,x);
}
}
return 0;
}

/*
4 4
1 2
2 3
3 4
Q 3
C 2
C 1
Q 3

*/