assignment_postmidsem_2

#include <bits/stdc++.h>
using namespace std;

struct point
{
    int x, y;
};

bool com(point p1, point p2)
{
    if (p1.x == p2.x)
        return p1.y < p2.y;
    return p1.x < p2.x;
}

int cross(point p1, point p2, point p3)
{
    return (p3.x - p1.x) * (p2.y - p1.y) - (p2.x - p1.x) * (p3.y - p1.y);
}
int main()
{
    int t;
    cin >> t;
    point pt[t];
    for (int i = 0; i < t; i++)
    {
        cin >> (pt[i].x) >> (pt[i].y);
    }
    sort(pt, pt + t, com);

    int k = 0;
    point v[t * 2];
    for (int i = 0; i < t; i++)
    {
        while (k >= 2 && (cross(v[k - 2], v[k - 1], pt[i]) <= 0))
            k--;
        v[k].x = pt[i].x;
        v[k].y = pt[i].y;
        k++;
    }
    int j = k + 1;
    for (int i = t - 1; i >= 0; i--)
    {
        while (k >= j && (cross(v[k - 2], v[k - 1], pt[i]) <= 0))
            k--;
        v[k].x = pt[i].x;
        v[k].y = pt[i].y;
        k++;
    }
    // cout << k;
    for (int i = 0; i < k - 1; i++)
        cout << (v[i].x) << " " << (v[i].y) << endl;
    return 0;
}