Closest points

#include <float.h>
#include <math.h>
#include <stdlib.h>

#include <algorithm>
#include <climits>
#include <iomanip>
#include <iostream>
#include <set>
#include <vector>
using namespace std;

#define ll long long int

struct Point {
    ll x, y;
};

bool compareX(const Point& p1, const Point& p2) {
    return (p1.x != p2.x) ? (p1.x - p2.x) : (p1.y - p2.y);
}

long long
closestPair(vector<pair<long long, long long> > coordinates,
            int n) {
    sort(coordinates.begin(), coordinates.end());

    set<pair<long long, long long> > s;

    long long squaredDistance = LLONG_MAX;
    long long j = 0;

    for (long long i = 0; i < n; ++i) {
        long long D = ceil(sqrt(squaredDistance));
        while (coordinates[i].first - coordinates[j].first >= D) {
            s.erase({coordinates[j].second, coordinates[j].first});
            j += 1;
        }

        auto start = s.lower_bound({coordinates[i].second - D,
                                    coordinates[i].first});
        auto end = s.upper_bound({coordinates[i].second + D,
                                  coordinates[i].first});

        for (auto it = start; it != end; ++it) {
            long long dx = coordinates[i].first - it->second;
            long long dy = coordinates[i].second - it->first;
            squaredDistance = min(squaredDistance, 1LL * dx * dx + 1LL * dy * dy);
        }

        s.insert({coordinates[i].second,
                  coordinates[i].first});
    }
    return squaredDistance;
}

int main() {
    int n;
    cin >> n;
    vector<pair<long long, long long> > P(n);
    vector<Point> points(n);
    for (int i = 0; i < n; i++) {
        pair<long long, long long> p = {0, 0};
        cin >> p.first;
        cin >> p.second;
        P[i] = p;
    }

    cout << fixed << closestPair(P, n) << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED