2 Closest Points in 2D Plane (N log^2 N).cpp

#include <bits/stdc++.h>
using namespace std;
struct Point
{
	int x, y;

	Point operator-(Point p)
	{
		return {x - p.x, y - p.y};
	}

	int dist()
	{
		return x * x + y * y;
	}
};

bool by_x(Point &a, Point &b)
{
	return a.x < b.x;
}

bool by_y(Point &a, Point &b)
{
	return a.y < b.y;
}

int n, ans = 1e18;
int a[N], pref[N];
Point pt[N];

int solve(int L, int R)
{
	if (L == R)
		return 1e18;
	int M = (L + R) / 2;
	sort(pt + L, pt + R + 1, by_x);
	int d = min(solve(L, M), solve(M + 1, R));
	int midx = pt[L + (R - L + 1) / 2].x;
	vector<Point> v;
	for (int i = L; i <= R; i++)
	{
		if (Point{pt[i].x - midx, 0}.dist() < d)
		{
			v.push_back(pt[i]);
		}
	}
	sort(v.begin(), v.end(), by_y);
	for (int i = 0; i < v.size(); i++)
	{
		for (int j = i + 1; j < v.size(); j++)
		{
			if (Point{0, v[i].y - v[j].y}.dist() > d)
				break;
			d = min(d, (v[i] - v[j]).dist());
		}
	}
	return d;
}

Problem 1 : http :					  //codeforces.com/contest/429/problem/D
				   Solution 1 : http: //codeforces.com/contest/429/submission/39494778