题解 | 动态整数集最近值提取

#include <iostream>
#include <math.h>
#include <set>
using namespace std;

set<int> s;

void Y(int x)
{
    cout << x << endl;
    s.erase(x);
}

int main() {
    int q;
    cin >> q;
    while(q--)
    {
        int op, x;
        cin >> op >> x;
        if (op == 1)
        {
            if (s.find(x) == s.end()) s.insert(x);
            else cout << "Already Exist" << endl;
        }
        else
        {
            if (s.empty()) cout << "Empty" << endl;
            else if (x < *s.begin()) Y(*s.begin());
            else if (x > *s.rbegin()) Y(*s.rbegin());
            else
            {
                auto lb = s.lower_bound(x);
                if (*lb == x)
                {
                    Y(x);
                    continue;
                }
                else lb--;
                auto ub = s.upper_bound(x);
                if (x - *lb <= *ub - x) Y(*lb);
                else Y(*ub);
            }
        }
    }
    return 0;
}
// 64 位输出请用 printf("%lld")