新代码：
```cpp
#include <iostream>
#define MAXN 100000
#define INF 0x7f7f7f7f
#define QWQ cout << "QWQ" << endl;
using namespace std;
struct Splay {
struct node{
int val, fa, siz, son[2], cnt;
} T[MAXN+10];
int tot, root;
int LorR(int x) {
return ((T[T[x].fa].son[0] == x) ? (0) : (1));
}
void connect(int x, int fa, int vis) {
T[fa].son[vis] = x;
T[x].fa = fa;
}
void updata(int x) {
T[x].siz = T[T[x].son[0]].siz + T[T[x].son[1]].siz + T[x].cnt;
}
void rotate(int x) {
int y = T[x].fa, r = T[T[x].fa].fa;
int ys = LorR(x), rs = LorR(y), B = T[x].son[ys^1];
connect(B, y, ys), connect(y, x, ys^1), connect(x, r, rs);
updata(y), updata(x);
}
void splay(int x, int to) {
while(T[x].fa != to) {
if(T[x].fa == to) break;
if(to == T[T[x].fa].fa) rotate(x);
else if(LorR(x) == LorR(T[x].fa)) rotate(T[x].fa), rotate(x);
else rotate(x), rotate(x);
}
if(!to) root = x;
}
int New(int val, int fa) {
tot++, T[tot].fa = fa, T[tot].val =val;
T[tot].siz = T[tot].cnt = 1;
return tot;
}
void find(int val) {
int now = root;
while(T[now].son[val > T[now].val] && val != T[now].val)
now = T[now].son[val > T[now].val];
splay(now, 0);
}
void insert(int val) {
int now = root;
if(!now)
root = New(val, 0);
else {
while(233) {
T[now].siz++;
if(T[now].val == val) {
T[now].cnt++;
splay(now, 0); tot++;
return ;
}
int next = ((val < T[now].val) ? (0) : (1));
if(!T[now].son[next]) {
T[now].son[next] = New(val, now);
splay(tot, 0);
return ;
}
now = T[now].son[next];
}
}
}
int low_up(int val, int f) {
find(val);
if(T[root].val > val && f) return root;
if(T[root].val < val && !f) return root;
int now = T[root].son[f];
while(T[now].son[f ^ 1])
now = T[now].son[f ^ 1];
return now;
}
int upper(int val) {
return T[low_up(val, 0)].val;
}
int lower(int val) {
return T[low_up(val, 1)].val;
}
int find_rank(int val) {
find(val);
return T[T[root].son[0]].siz;
}
int find_val(int rank) {
int now = root;
while(233) {
if(rank <= T[T[now].son[0]].siz) now = T[now].son[0];
else if(rank <= T[T[now].son[0]].siz + T[now].cnt) return T[now].val;
else rank = rank - T[T[now].son[0]].siz - T[now].cnt, now = T[now].son[1];
}
}
void clear(int x) {
T[x].cnt = T[x].siz = T[x].son[0] = T[x].son[1] = T[x].val = T[x].fa = 0;
}
void erase(int val) {
int pre = low_up(val, 0), low = low_up(val, 1);
splay(pre, 0), splay(low, pre);
int u = T[low].son[0];
if(T[u].cnt > 1) {
T[u].cnt--;
splay(u, 0);
}
else T[u].son[0] = 0;
}
}qwq;
int main() {
qwq.insert(INF);
qwq.insert(-INF);
int T, opt, val;
cin >> T;
while(T--) {
cin >> opt >> val;
if(opt == 1) qwq.insert(val);
else if(opt == 2) qwq.erase(val);
else if(opt == 3) cout << qwq.find_rank(val) << endl;
else if(opt == 4) cout << qwq.find_val(val + 1) << endl;
else if(opt == 5) cout << qwq.upper(val) << endl;
else if(opt == 6) cout << qwq.lower(val) << endl;
}
}
```
by SIXIANG32 @ 2021-07-07 15:22:39