p2596 书架（Treap）

写平衡树修锅快修到死系列
我太蠢了
其实是平衡树裸体裸题
插入，删除，交换前驱或后继，查询rank和kth
维护一个pos数组，表示第i个书的编号
然后注意许许多多的细节，没了

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
struct Node{
    int lson,rson,ran,val,w,sz;
}Treap[80000<<2];
int pos[80100],Lx,Rx,Nodecnt,n,m,root;
void pushup(int o){
    Treap[o].sz=Treap[Treap[o].lson].sz+Treap[Treap[o].rson].sz+1;
}
void rotateR(int &o){
    int k=Treap[o].lson;
    Treap[o].lson=Treap[k].rson;
    Treap[k].rson=o;
    Treap[k].sz=Treap[o].sz;
    pushup(o);
    o=k;
}
void rotateL(int &o){
    int k=Treap[o].rson;
    Treap[o].rson=Treap[k].lson;
    Treap[k].lson=o;
    Treap[k].sz=Treap[o].sz;
    pushup(o);
    o=k;
}
int NewNode(int cx,int wl){
    ++Nodecnt;
    Treap[Nodecnt].sz=1;
    Treap[Nodecnt].lson=Treap[Nodecnt].rson=0;
    Treap[Nodecnt].ran=rand();
    Treap[Nodecnt].val=wl;
    Treap[Nodecnt].w=cx;
    return Nodecnt;
}
void insert(int &o,int cx,int wl){
    if(!o){
        o=NewNode(cx,wl);
        return;
    }
    Treap[o].sz++;
    if(wl<=Treap[o].val){
        insert(Treap[o].lson,cx,wl);
        if(Treap[Treap[o].lson].ran<Treap[o].ran)
            rotateR(o);
        // pushup(o);
    }
    else{
        insert(Treap[o].rson,cx,wl);
        if(Treap[Treap[o].rson].ran<Treap[o].ran)
            rotateL(o);
        // pushup(o);
    }
}
void erase(int &o,int wl){
    if(!o)
        return;
    if(Treap[o].val==wl){
        if(Treap[o].lson==0||Treap[o].rson==0){
            o=Treap[o].lson+Treap[o].rson;
            return;
        }
        if(Treap[Treap[o].lson].ran<Treap[Treap[o].rson].ran){
            rotateR(o);
            erase(o,wl);
        }
        else{
            rotateL(o);
            erase(o,wl);
        }
        pushup(o);
        return;
    }
    Treap[o].sz--;
    if(wl<=Treap[o].val){
        erase(Treap[o].lson,wl);
        pushup(o);
    }
    else{
        erase(Treap[o].rson,wl);
        pushup(o);
    }
}
int ranks(int o,int wl){
    if(!o)
        return 0;
    if(wl==Treap[o].val){
        return Treap[Treap[o].lson].sz+1;
    }
    if(wl<=Treap[o].val){
        return ranks(Treap[o].lson,wl);
    }   
    else{
        return ranks(Treap[o].rson,wl)+Treap[Treap[o].lson].sz+1;
    } 
}
int kth(int k,int o){
    if(k==0)
        return 0;
    if(k==Treap[Treap[o].lson].sz+1)
        return Treap[o].w;
    if(k<=Treap[Treap[o].lson].sz)
        return kth(k,Treap[o].lson);
    else
        return kth(k-Treap[Treap[o].lson].sz-1,Treap[o].rson);
}
int pre(int wl){
    return kth(ranks(root,wl)-1,root);
}
int back(int wl){
    return kth(ranks(root,wl)+1,root);
}
int main(){
    Lx=1;
    // freopen("7.in","r",stdin);
    // freopen("test.out","w",stdout);
    srand(19260817);
    scanf("%d %d",&n,&m);
    for(int i=1;i<=n;i++){
        int x;
        scanf("%d",&x);
        ++Rx;
        pos[x]=Rx;
        insert(root,x,Rx);
    }
    char opt[20];
    int sx,tx;
    for(int i=1;i<=m;i++){
        scanf("%s",opt);
        if(opt[0]=='T'){
            scanf("%d",&sx);
            erase(root,pos[sx]);
            Lx--;
            pos[sx]=Lx;
            insert(root,sx,Lx);
        }
        else if(opt[0]=='B'){
            scanf("%d",&sx);
            erase(root,pos[sx]);
            Rx++;
            pos[sx]=Rx;
            insert(root,sx,Rx);
        }
        else if(opt[0]=='I'){
            scanf("%d %d",&sx,&tx);
            if(tx==0)
                continue;
            if(tx==1){
                int need=back(pos[sx]);
                erase(root,pos[sx]);
                erase(root,pos[need]);
                swap(pos[sx],pos[need]);
                insert(root,sx,pos[sx]);
                insert(root,need,pos[need]);   
            }
            if(tx==-1){
                int need=pre(pos[sx]);
                erase(root,pos[sx]);
                erase(root,pos[need]);
                swap(pos[sx],pos[need]);
                insert(root,sx,pos[sx]);
                insert(root,need,pos[need]);
            }
        }
        else if(opt[0]=='A'){
            scanf("%d",&sx);
            printf("%d
",ranks(root,pos[sx])-1);
        }
        else if(opt[0]=='Q'){
            scanf("%d",&sx);
            printf("%d
",kth(sx,root));
        }
    }
    return 0;
}