For this input:

5

0 0

1 1

2 2

3 3

4 4

it shows 0 where the answer is 1.4142135623730951

#include

using namespace std;

const int N = 1e5 + 5;

struct Point { double x, y; bool operator<(const Point &p) const { return x < p.x || (x == p.x && y < p.y); } } points[N];

double dist(Point a, Point b) { double dx = a.x - b.x, dy = a.y - b.y; return sqrt(dx * dx + dy * dy); }

double closestPair(int l, int r) { if (l >= r) return 1e9; if (l + 1 == r) return dist(points[l], points[r]);

int mid = l + r >> 1; double d = min(closestPair(l, mid), closestPair(mid + 1, r));

int i = l, j = mid + 1, k = 0; Point strip[r - l + 1]; while (i <= mid && j <= r) { if (points[i] < points[j]) strip[k++] = points[i++]; else strip[k++] = points[j++]; } while (i <= mid) strip[k++] = points[i++]; while (j <= r) strip[k++] = points[j++]; for (int i = 0; i < k; i++) points[l + i] = strip[i];

i = 0; for (int j = l; j <= r; j++) { if (abs(points[j].x - points[mid].x) >= d) continue; while (i < k - 1 && points[l + i + 1].y < points[j].y) i++; for (int t = i; t < k && points[l + t].y - points[j].y < d; t++) { d = min(d, dist(points[l + t], points[j])); } }

return d; }

int main() { int n; cin >> n; for (int i = 0; i < n; i++) { cin >> points[i].x >> points[i].y; } sort(points, points + n); cout << closestPair(0, n - 1) << endl; return 0; }