BZOJ 3223 Splay区间翻转

思路：
区间翻转的裸题 终于tm理解splay了……

//By SiriusRen
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define N 155555
int n,m,root,size
,ch
[2],fa
,rev
,v
;
void push_up(int x){size[x]=size[ch[x][0]]+size[ch[x][1]]+1;}
int build(int l,int r){
if(l>r)return 0;
if(l==r){size[l]=1,v[l]=l-1;return l;}
int mid=(l+r)>>1;v[mid]=mid-1;
ch[mid][0]=build(l,mid-1);fa[ch[mid][0]]=mid;
ch[mid][1]=build(mid+1,r);fa[ch[mid][1]]=mid;
push_up(mid);
return mid;
}
void rotate(int p){
int q=fa
,y=fa[q],f=(ch[q][1]==p);
ch[q][f]=ch[p][!f],fa[ch[q][f]]=q;
ch[p][!f]=q;fa[q]=p;fa[p]=y;
if(y){
if(ch[y][0]==q)ch[y][0]=p;
else ch[y][1]=p;
}push_up(q);
}
void Splay(int x,int tp){
for(int y;y=fa[x];rotate(x)){
if(y==tp)break;
if(fa[y]!=tp){
if((ch[y][0]==x)^(ch[fa[y]][0]==y))rotate(x);
else rotate(y);
}
}push_up(x);
if(!tp)root=x;
}
void push_down(int x){
if(rev[x]){
rev[ch[x][0]]^=1,rev[ch[x][1]]^=1;
swap(ch[x][0],ch[x][1]);
rev[x]=0;
}
}
int find(int x,int num){
push_down(x);
int sz=size[ch[x][0]];
if(sz+1==num)return x;
else if(sz+1>num)return find(ch[x][0],num);
else return find(ch[x][1],num-sz-1);
}
void reverse(int l,int r){
int y=find(root,l);Splay(y,0);
Splay(find(root,r+2),y);
rev[ch[ch[root][1]][0]]^=1;
}
void dfs(int x){
push_down(x);
if(ch[x][0])dfs(ch[x][0]);
if(v[x]&&v[x]!=n+1)printf("%d ",v[x]);
if(ch[x][1])dfs(ch[x][1]);
}
int main(){
scanf("%d%d",&n,&m);
root=build(1,n+2);
for(int i=1;i<=m;i++){
int l,r;
scanf("%d%d",&l,&r);
reverse(l,r);
}
dfs(root);
}