判断最左边的右端点和最右边的左端点 如果小于，则不相交

#include <iostream>
#include <vector>
#include <set>
using namespace std;
#define int long long
const int mod=1e+7;
signed main() {
    iostream::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin >> n;
    multiset<int> l, r;

    for (int i = 1; i <= n; i++) {
        char c;
        cin >> c;
        int x, y;
        cin >> x >> y;
        if (c == '+') {
            l.insert(x);
            r.insert(y);
        } else {
            l.erase(l.find(x));
            r.erase(r.find(y));
        }
        if (l.size() > 1 && (*r.begin() < *l.rbegin())) {
            cout << "YES" << endl;
        } else {
            cout << "NO" << endl;
        }
    }
    return 0;
 }