二分法，对y轴归并排序。

#include <iostream>
#include<string>
#include<cmath>
#include<iomanip>
#include<vector>
#include<limits.h>
#include<algorithm>
using namespace std;

const int num = 400010;
struct node {
	long long x, y;
}poi[num];
int n;
int may[num];

bool cmp1(node a, node b) {
	return a.x < b.x;
}
bool cmp2(node a, node b) {
	return a.y<b.y;
}
long long dis(node a, node b) {
	return (a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y);
}
long long  solve(int l, int r) {
	if (l == r)return LLONG_MAX;
	else if (l + 1 == r) {
		if (poi[l].y > poi[r].y)swap(poi[l], poi[r]);
		return dis(poi[l], poi[r]);
	}
	int mid = 1+(l + r) / 2;
	long long  le = solve(l, mid-1);
	long long  ri = solve(mid , r);
	long long  mi = min(le, ri);
	inplace_merge(poi+l,poi+mid,poi+r+1, cmp2);
	int k = 0;
	for (int i = l; i <=r; i++) {
		if (fabs(poi[i].x - poi[mid].x) < mi) {
			may[k++] = i;
		}
	}
	
	for (int i = 0; i < k; i++) {
		for (int j = i + 1; j <= i + 5&&j<k; j++) {
			mi = min(mi, dis(poi[may[i]], poi[may[j]]));
		}
	}
	return mi;
}
int main()
{
	cin >> n;
	for (int i=0; i < n; i++)cin >> poi[i].x >> poi[i].y;
	sort(poi, poi + n, cmp1);
	cout<<solve(0, n - 1);
}