题解 | 动态整数集最近值提取

///之前因为没有及时continue导致了迭代器失效 和 逻辑穿透
#include <iostream>
#include <set>
using namespace std;

set<int> s;

int main() {
    int x, q, op;
    cin >> q;
    while (q--) {
        cin >> op >> x;
        if (op == 1) {

            if (s.count(x))
            {
                cout << "Already Exist" << endl;
            } 
            else {
                s.insert(x);
            }
        }
        else if (op == 2)
        {
            if (s.empty()) {
                cout << "Empty" << endl;
                continue;
            }
            if(x <= *s.begin())
            {
                cout << *s.begin() << endl;
                s.erase(*s.begin());
                continue;
            }
            else if(x >= *(--s.end()))
            {
                cout << *(--s.end()) << endl;
                s.erase(*(--s.end()));
                continue;
            }

            int  a,b;
            auto it = s.lower_bound(x);
            a = *it;
            b = *--it;
            if(abs(a-x)>=abs(x-b))
            {
                cout << b << endl;
                s.erase(b);
            }
            else {
                cout << a << endl;
                s.erase(a);
            }                         
        }
    }
    return 0;
}