Closest points

#include <bits/stdc++.h>
#include <climits>

using namespace std;

struct Point {
    long long x, y;
};

bool mysort(Point &a, Point &b) {
    if (a.x == b.x)
        return a.y < b.y;
    else
        return a.x < b.x;
}

long long euclidean_distance(Point &a, Point &b) {
    return (a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y);
}

bool in_region(Point &a, Point &b, long long mindist) {
    return (a.x - b.x) * (a.x - b.x) <= mindist;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int n;
    cin >> n;

    vector<Point> v(n);

    for (int i = 0; i < n; ++i) {
        cin >> v[i].x >> v[i].y;
    }

    sort(v.begin(), v.end(), mysort);

    long long mindist = euclidean_distance(v[0], v[1]);

    for (int i = 1; i < n; ++i) {
        int j = i - 1;
    
        while (j >= 0 and in_region(v[i], v[j], mindist)) {
            long long ec = euclidean_distance(v[j], v[i]);
            if (ec < mindist) {
                mindist = ec;
            }
            --j;
        }
    }
    cout << mindist << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: TIME LIMIT EXCEEDED

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: TIME LIMIT EXCEEDED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED