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[N],ch[N][2],fa[N],rev[N],v[N];
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[p],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);
}