权值线段树模板

【模板】普通平衡树

//  AC one more times

#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define pb push_back
#define endl '\n'
#define all(x) (x).begin(), (x).end()
typedef pair<int, int> pii;

const int N = 1e5 + 10;

struct segtree
{
	int s;
}seg[N * 4];
int n;
vector<int> vx;
pii a[N];
multiset<int> s;

void update(int id)
{
	seg[id].s = seg[id * 2].s + seg[id * 2 + 1].s;
}

void change(int id, int l, int r, int pos, int val)
{
	if(l == r)
	{
		seg[id].s = seg[id].s + val;
		return;
	}
	int mid = (l + r) >> 1;
	if(pos <= mid)
		change(id * 2, l, mid, pos, val);
	else
		change(id * 2 + 1, mid + 1, r, pos, val);
	update(id);
}

int query1(int id, int l, int r, int ql, int qr)
{
	if(ql > qr)	return 0;
	if(l == ql && r == qr)
	{
		return seg[id].s;
	}
	int mid = (l + r) >> 1;
	if(qr <= mid)
		return query1(id * 2, l, mid, ql, qr);
	else if(ql > mid)
		return query1(id * 2 + 1, mid + 1, r, ql, qr);
	else 
		return query1(id * 2, l, mid, ql, mid) +
				query1(id * 2 + 1, mid + 1, r, mid + 1, qr);
}

int query2(int id, int l, int r, int x)
{
	if(l == r)
	{
		return l;
	}
	int mid = (l + r) >> 1;
	if(seg[id * 2].s >= x)
		return query2(id * 2, l, mid, x);
	else
		return query2(id * 2 + 1, mid + 1, r, x - seg[id * 2].s);
}

void solve()
{   
	cin>>n;
	for(int i = 1; i <= n; i++)
	{
		cin>>a[i].fi>>a[i].se;
		if(a[i].fi != 4)
			vx.pb(a[i].se);
	}
	sort(all(vx));
	vx.erase(unique(vx.begin(), vx.end()), vx.end());
	for(int i = 1; i <= n; i++)
	{
		int opt = a[i].fi, x = a[i].se;
		x = lower_bound(vx.begin(), vx.end(), x) -vx.begin() + 1;
		if(opt == 1)
		{
			change(1, 1, n, x, 1);
			s.insert(vx[x - 1]);
		}
		else if(opt == 2)
		{
			change(1, 1, n, x, -1);
			s.erase(s.find(vx[x - 1]));
		}
		else if(opt == 3)
			cout<<query1(1, 1, n, 1, x - 1) + 1<<endl;
		else if(opt == 4)
			cout<<vx[query2(1, 1, n, a[i].se) - 1]<<endl;
		else if(opt == 5)
			cout<<*(--s.lower_bound(vx[x - 1]))<<endl;
		else
			cout<<*(s.upper_bound(vx[x - 1]))<<endl;
	}
	
}

int main()
{
    std::ios::sync_with_stdio(false);   cin.tie(nullptr), cout.tie(nullptr);
    
    int TC = 1;
    
    //cin >> TC;    
    for(int tc = 1; tc <= TC; tc++)
    {
        //cout << "Case #" << tc << ": ";         
        solve();
    }


    return 0;
}