[ZJOI2006]书架

链接：https://www.luogu.org/problemnew/show/P2596

题解：

写了两天的平衡树终于大概弄好了所有模板（模板不熟写错debug真是要死）

对于放在头尾，只需要删除，再在头/尾插入就可以了

对于交换，就交换一下映射

代码：

#include <bits/stdc++.h>
#define maxn 100000
using namespace std;
int n,m,data[maxn],count2[maxn],leftson[maxn],rightson[maxn],fa[maxn],a[maxn],
    point[maxn],num,root;
void updata(int x)
{
    count2[x]=count2[leftson[x]]+count2[rightson[x]]+;
}
void rotate(int x,int y)
{
    int father=fa[x];
    if (y==)
    {
        rightson[father]=leftson[x];
        if (leftson[x]) fa[leftson[x]]=father;
    } else
    {
        leftson[father]=rightson[x];
        if (rightson[x]) fa[rightson[x]]=father;
    }
    fa[x]=fa[father];
    if (fa[father])
    {
        if (leftson[fa[father]]==father)
          leftson[fa[father]]=x;
        else rightson[fa[father]]=x;
    }
    fa[father]=x;
    if (y==) leftson[x]=father; else rightson[x]=father;
    updata(father); updata(x);
}
void splay(int x,int goal)
{
    if (x==root) return;
    int father=fa[x];
    while (father!=goal)
    {
        if (fa[father]==goal)
        {
            if (x==leftson[father]) rotate(x,); else rotate(x,);
        } else
        {
            if (father==leftson[fa[father]])
            {
                if (x==leftson[father]) rotate(father,),rotate(x,);
                else rotate(x,),rotate(x,);
            } else
            {
                if (x==rightson[father]) rotate(father,),rotate(x,);
                else rotate(x,),rotate(x,);
            }
        }
        father=fa[x];
    }
    if (goal==) root=x;
}
#define mid (h+t)/2
void build(int h,int t,int father,bool x,int a[maxn])
{
  count2[++num]=; data[num]=a[mid]; fa[num]=father;
  point[a[mid]]=num;
  if (father)
  {
      if (x==) leftson[father]=num; else rightson[father]=num;
    }
    int tmp=num;
    if (h<mid) build(h,mid-,tmp,,a);
    if (mid<t) build(mid+,t,tmp,,a);
    updata(tmp);
}
int search(int goal)
{
    int x=root,cnt=;
    while (x)
    {
        if (cnt+count2[leftson[x]]==goal) return(x);
        if (count2[leftson[x]]+cnt<goal)
        {
            cnt+=count2[leftson[x]]+; x=rightson[x];
        } else
        {
            x=leftson[x];
        }
    }
}
void delete1()
{
    int x=leftson[root];
    if (x==)
    {
        root=rightson[root]; fa[root]=; return;
    }
    while (rightson[x]) x=rightson[x];
    splay(x,root);
    rightson[x]=rightson[root];
    if (rightson[root]) fa[rightson[root]]=x;
    updata(x);
    root=x; fa[x]=;
}
void insert1(int x)
{
    int y=root;
    while (leftson[y]) count2[y]++,y=leftson[y]; count2[y]++;
    leftson[y]=x; fa[x]=y; leftson[x]=; rightson[x]=; count2[x]=;
}
void insert2(int x)
{
    int y=root;
    while (rightson[y]) count2[y]++,y=rightson[y]; count2[y]++;
    rightson[y]=x; fa[x]=y; rightson[x]=; leftson[x]=; count2[x]=;
}
void print(int x)
{
    if (leftson[x]) print(leftson[x]);
    cout<<data[x]<<" ";
    if (rightson[x]) print(rightson[x]);
}
char c[];
int main()
{
   freopen("noip.in","r",stdin);
     freopen("noip.out","w",stdout);
     cin>>n>>m;
     for (int i=;i<=n;i++)
     {
           cin>>a[i];
     }
     build(,n,,,a); root=;
     for (int i=;i<=m;i++)
     {
    //         print(root); cout<<i-1<<endl;
           cin>>c; int d,e;
           if (c[]=='T')
           {
                cin>>d; int x=point[d]; splay(x,);
                 delete1();

                  insert1(x);
            }
            if (c[]=='B')
            {
                cin>>d; int x=point[d]; splay(x,);
                 delete1();
                 insert2(x);
            }
            if (c[]=='I')
            {
                cin>>d>>e;
                if (e!=)
                {
                   int x1=point[d]; splay(x1,);
                   int x2=search(count2[leftson[x1]]++e);
                   swap(point[d],point[data[x2]]);
                   swap(data[x2],data[x1]);
                }
            }
            if (c[]=='A')
            {
                cin>>d; int x=point[d];
                splay(x,);
                cout<<count2[leftson[x]]<<endl;
            }
            if (c[]=='Q')
            {
                cin>>d; int x=search(d);
                cout<<data[x]<<endl;
            }
     }
}