rt，指针版的 fhq-treap，空指针的都查过了 /kel

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

mt19937 eng(time(0));
uniform_int_distribution<int> dist;

typedef struct node {
	
	int w, val, s;
	node *l, *r;
	
	node(int val = 0, int s = 0) : 
	val(val), s(s), l(nullptr), r(nullptr), w(dist(eng)) {}
	~node() { delete l, r; }
	
	int size() {
		if (this) return s;
		return 0;
	}
	
	void pushup() {
		s = l->size() + r->size() + 1;
	}

} *nodeptr; nodeptr rt;

void split(nodeptr p, int val, nodeptr &x, nodeptr &y) {
	if (!p) return x = y = nullptr, void();
	if (p->val <= val) x = p, split(x->r, val, x->r, y);
	else y = p, split(y->l, val, x, y->l); p->pushup();
}

nodeptr merge(nodeptr x, nodeptr y) {
	if (!x || !y) return x == nullptr ? y : x;
	if (x->w < y->w) return x->r = merge(x->r, y), x->pushup(), x;
	return y->l = merge(x, y->l), y->pushup(), y;
}

inline 
void insert(int val) {
	nodeptr l = nullptr, r = nullptr; split(rt, val, l, r);
	rt = merge(merge(l, new node(val, 1)), r);
}

inline 
void erase(int val) {
	nodeptr l = nullptr, r = nullptr, p = nullptr;
	split(rt, val, l, r), split(l, val - 1, l, p);
	rt = merge(merge(l, merge(p->l, p->r)), r);
}

inline 
int rnk(int val) {
	int ans; nodeptr l = nullptr, r = nullptr;
	split(rt, val - 1, l, r), ans = l->size();
	return rt = merge(l, r), ans + 1;
}

inline 
int kth(int k) {
	for (nodeptr p = rt; p;) {
		if (p->l->size() >= k) p = p->l;
		else if (p->l->size() + 1 == k) return p->val;
		else k -= p->l->size() + 1, p = p->r;
	}
	return -1;
}

inline 
int find(int val, int f) {
	nodeptr l = nullptr, r = nullptr, p = nullptr;
	split(rt, val - f, l, r);
	if (f) for (p = l; p->r; p = p->r);
	else for (p = r; p->l; p = p->l);
	return rt = merge(l, r), p->val;
}

int n;

int main() {
	scanf("%d", &n);
	for (int opt, x; n--;) {
		scanf("%d%d", &opt, &x);
		switch (opt) {
		case 1 : insert(x); break;
		case 2 : erase(x); break;
		case 3 : printf("%d\n", rnk(x)); break;
		case 4 : printf("%d\n", kth(x)); break;
		case 5 : printf("%d\n", find(x, 1)); break;
		case 6 : printf("%d\n", find(x, 0)); break;
		}
	}
}