思路：搞搞平衡树。



#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PII pair<int, int>
#define y1 skldjfskldjg
#define y2 skldfjsklejg
using namespace std;

const int N = 4e5 + 7;
const int M = 5e5 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 45989;
const int B = 1e5;

int val[N], hs[N], n, m;
char s[10];
struct node {
    node* ch[2];
    int key, fix, sz, cnt;
    void update() {
        sz = ch[0]->sz + ch[1]->sz + cnt;
    }
};

typedef node* P_node;

struct Treap {
    node base[N], nil;
    P_node root, null, len;

    Treap() {
        root = null = &nil;
        null->key = null->fix = 1e9;
        null->sz = null->cnt = 0;
        null->ch[0] = null->ch[1] = null;
        len = base;
    }

    P_node newnode(int tkey) {
        len->key = tkey;
        len->fix = rand();
        len->ch[0] = len->ch[1] = null;
        len->sz = len->cnt = 1;
        return len++;
    }

    void rot(P_node &p, int d) {
        P_node k = p->ch[d ^ 1];
        p->ch[d ^ 1] = k->ch[d];
        k->ch[d] = p;
        p->update();
        k->update();
        p = k;
    }

    void _Insert(P_node &p, int tkey) {
        if(p == null) {
            p = newnode(tkey);
        } else if(p->key == tkey) {
            p->cnt++;
        } else {
            int d = tkey > p->key;
            _Insert(p->ch[d], tkey);
            if(p->ch[d]->fix > p->fix) {
                rot(p, d ^ 1);
            }
        }
        p->update();
    }

    void _Delete(P_node &p, int tkey) {
        if(p == null) return;
        if(p->key == tkey) {
            if(p->cnt > 1) p->cnt--;
            else if(p->ch[0] == null) p = p->ch[1];
            else if(p->ch[1] == null) p = p->ch[0];
            else {
                int d = p->ch[0]->fix > p->ch[1]->fix;
                rot(p, d);
                _Delete(p->ch[d], tkey);
            }
        } else {
            _Delete(p->ch[tkey > p->key], tkey);
        }
        p->update();
    }

    int _Kth(P_node p, int k) {
        if(p == null || k < 1 || k > p->sz) return 0;
        if(k < p->ch[0]->sz + 1) return _Kth(p->ch[0], k);
        if(k > p->ch[0]->sz + p->cnt) return _Kth(p->ch[1], k - p->ch[0]->sz - p->cnt);
        return p->key;
    }

    int _Rank(P_node p, int tkey, int res) {
        if(p == null) return -1;
        if(p->key == tkey) return p->ch[0]->sz + res + 1;
        if(tkey < p->key) return _Rank(p->ch[0], tkey, res);
        return _Rank(p->ch[1], tkey, res + p->ch[0]->sz + p->cnt);
    }

    int _Pred(P_node p, int tkey){
        if(p == null) return -1e9;
        if(tkey <= p->key) return _Pred(p->ch[0], tkey);
        return max(p->key, _Pred(p->ch[1], tkey));
    }

    int _Succ(P_node p, int tkey){
        if(p == null) return 1e9;
        if(tkey >= p->key) return _Succ(p->ch[1], tkey);
        return min(p->key, _Succ(p->ch[0], tkey));
    }


    void Insert(int tkey){ _Insert(root,tkey); }
    void Delete(int tkey){ _Delete(root,tkey); }
    int Kth(int k){ return _Kth(root,k); }
    int Rank(int tkey){ return _Rank(root,tkey,0); }
    int Pred(int tkey){ return _Pred(root,tkey); }
    int Succ(int tkey){ return _Succ(root,tkey); }
}tp;
int main() {
    scanf("%d%d", &n, &m);
    int mx = n + B, mn = 1 + B;
    for(int i = 1; i <= n; i++) {
        int x; scanf("%d", &x);
        val[x] = i + B;
        hs[i + B] = x;
        tp.Insert(i + B);
    }

    while(m--) {
        int id, t;
        scanf("%s", s);
        if(s[0] == 'T') {
            scanf("%d", &id);
            tp.Delete(val[id]);
            val[id] = --mn;
            hs[mn] = id;
            tp.Insert(val[id]);
        } else if(s[0] == 'B') {
            scanf("%d", &id);
            tp.Delete(val[id]);
            val[id] = ++mx;
            hs[mx] = id;
            tp.Insert(val[id]);
        } else if(s[0] == 'I') {
            scanf("%d%d", &id, &t);
            if(t == 1) {
                int z = tp.Succ(val[id]);
                if(z < -100000000 || z > 100000000) continue;
                int id2 = hs[z], v = val[id];
                swap(val[id], val[id2]);
                swap(hs[v], hs[z]);
            } else if(t == -1) {
                int z = tp.Pred(val[id]);
                if(z < -100000000 || z > 100000000) continue;
                int id2 = hs[z], v = val[id];
                swap(val[id], val[id2]);
                swap(hs[v], hs[z]);
            }
        } else if(s[0] == 'A'){
            scanf("%d", &id);
            printf("%d\n", tp.Rank(val[id]) - 1);
        } else {
            scanf("%d", &id);
            printf("%d\n", hs[tp.Kth(id)]);
        }
    }
    return 0;
}