RT，WA+1个TLE

#include <iostream>
#include <cstdio>
#include <algorithm>

#define rint register int
#define endl '\n'

const int N = 5e5 + 5;

int root, idx;

struct Splay
{
    struct Node
    {
        int s[2], fa;
        int val, cnt;
        int size; //儿子数量 
        void init(int _val, int _fa)
        {
            val = _val, fa = _fa;
            size = cnt = 1;
        }
        void clear()
        {
            s[0] = s[1] = 0;
            fa = 0;
            val = cnt = 0;
            size = 0;
        }
    } t[N];
    
    void push_up(int p)
    {
        t[p].size = t[t[p].s[0]].size + t[t[p].s[1]].size + 1;
    }

    void rotate(int x)
    {
        int y = t[x].fa;
        int z = t[y].fa;
        int k = t[y].s[1] == x;
        t[z].s[t[z].s[1] == y] = x;
        t[x].fa = z;
        t[y].s[k] = t[x].s[k ^ 1];
        t[t[x].s[k ^ 1]].fa = y;
        t[x].s[k ^ 1] = y;
        t[y].fa = x;
        push_up(y);
        push_up(x);
    }

    void splay(int x, int k)
    {
        while (t[x].fa != k)
        {
            int y = t[x].fa;
            int z = t[y].fa;
            if (z != k)
            {
                if ((t[y].s[1] == x) ^ (t[z].s[1] == y))
                {
                    rotate(x);
                }
                else
                {
                    rotate(y);
                }
            }
            rotate(x);
        }
        if (k == 0)
        {
            root = x;
        }
    }

    void insert(int k)
    {
        if (root == 0)
        {
            t[++idx].init(k, 0);
            root = idx;
            return;
        }
        int p = root, fa = 0;
        while (1)
        {
            if (t[p].val == k)
            {
                t[p].cnt++;
                push_up(p);
                push_up(fa);
                splay(p, 0);
                break;
            }
            fa = p;
            p = t[p].s[t[p].val < k];
            if (p == 0)
            {
                t[++idx].init(k, fa);
                t[fa].s[t[fa].val < k] = idx;
                push_up(fa);
                splay(idx, 0);
                break;
            }
        }
    }

    int find(int k)
    {
        int res = 0, p = root;
        while (1)
        {
            if (k < t[p].val)
            {
                p = t[p].s[0];
            }
            else
            {
                if (t[p].s[0])
                {
                    res += t[t[p].s[0]].size;
                }
                if (k == t[p].val)
                {
                    splay(p, 0);
                    return res + 1;
                }
                res += t[p].cnt;
                p = t[p].s[1];
            }
        }
    }

    int kth_number(int k)
    {
        int p = root;
        while (1)
        {
            if (t[t[p].s[0]].size >= k && t[p].s[0])
            {
                p = t[p].s[0];
            }
            else
            {
                k -= t[p].cnt;
                if (t[p].s[0])
                {
                    k -= t[t[p].s[0]].size;
                }
                if (k <= 0)
                {
                    splay(p, 0);
                    return t[p].val;
                }
                p = t[p].s[1];
            }
        }
    }

    int prev()
    {
        int p = t[root].s[0];
        if (p == 0)
        {
            return p;
        }
        while (t[p].s[1])
        {
            p = t[p].s[1];
        }
        splay(p, 0);
        return p;
    }

    int next()
    {
        int p = t[root].s[1];
        if (p == 0)
        {
            return p;
        }
        while (t[p].s[0])
        {
            p = t[p].s[0];
        }
        splay(p, 0);
        return p;
    }
    
    int get_prev()
    {
		return t[prev()].val;
	}
	
	int get_next()
	{
		return t[next()].val;
	}

    void del(int k)
    {
        find(k);
        if (t[root].cnt > 1)
        {
            t[root].cnt--;
            push_up(root);
            return;
        }
        if (!t[root].s[0] && !t[root].s[1])
        {
            t[root].clear();
            root = 0;
            return;
        }
        if (!t[root].s[0])
        {
            int p = root;
            root = t[root].s[1];
            t[root].fa = 0;
            t[p].clear();
            return;
        }
        if (!t[root].s[1])
        {
            int p = root;
            root = t[root].s[0];
            t[root].fa = 0;
            t[p].clear();
            return;
        }
        int p = root;
        int x = prev();
        t[t[p].s[1]].fa = x;
        t[x].s[1] = t[p].s[1];
        t[p].clear();
        push_up(root);
    }
} tree;

int n;

int main()
{
	scanf("%d", &n);
    while (n--)
    {
        int op, x;
        scanf("%d%d", &op, &x);
        if (op == 1)
            tree.insert(x);
        if (op == 2)
            tree.del(x);
        if (op == 3)
            printf("%d\n", tree.find(x));
        if (op == 4)
            printf("%d\n", tree.kth_number(x));
        if (op == 5)
            tree.insert(x), printf("%d\n", tree.get_prev()), tree.del(x);
        if (op == 6)
            tree.insert(x), printf("%d\n", tree.get_next()), tree.del(x);
    }
    return 0;
}