SMMR-247: Leakage

#include <bits/stdc++.h>

using namespace std;
using lli = long long;
const lli INF = 1e18;
using pl = pair <lli, lli>;
using pll = pair <lli, pl>;
set <lli> num;
priority_queue <pll, vector<pll>, greater<pll>> pq;

bool Have(lli x){
    return num.find(x) != num.end();
}

bool check(pll x){
    return Have(x.second.first) and Have(x.second.second);
}

void Del(){
    while(!pq.empty() and !check(pq.top())) pq.pop();
}

int main(){

    int q;
    scanf("%d", &q);

    for(int i=1;i<=q;i++){
        int opr;
        lli x;
        scanf("%d", &opr);
        if(opr == 1){
            scanf("%lld", &x);
            num.insert(x);
            auto it = num.find(x);
            if(it == num.begin() and it == num.end()) continue;
            if(it == num.begin()) pq.push({*next(it) - x, {x, *next(it)}});
            else if(it == num.end()) pq.push({x - *prev(it), {*prev(it), x}});
            else {
                pq.push({*next(it) - x, {x, *next(it)}});
                pq.push({x - *prev(it), {*prev(it), x}});
            }
        }
        else if(opr == 2){
            scanf("%lld", &x);
            auto it = num.find(x);
            if(it != num.begin() and it != num.end()) pq.push({*next(it) - *prev(it), {*prev(it), *next(it)}});
            num.erase(it);
        }
        else if(opr == 3){
            Del();
            printf("%lld\n", pq.top().first);
        }
        else if(opr == 4){
            printf("%lld\n", (lli) *num.rbegin() - *num.begin());
        }
    }

    return 0;
}