Broken car race

input/code.cpp: In lambda function:
input/code.cpp:59:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Point>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   59 |     for(int i=0; i<h.size(); i++) {
      |                  ~^~~~~~~~~

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

struct Point {
  long long x, y;
  Point() {}
  Point(long long x, long long y) : x(x), y(y) {}
  bool operator < (const Point &p) const {
    return x < p.x || (x == p.x && y < p.y);
  }
};

long long cross(const Point &O, const Point &A, const Point &B) {
  return (A.x - O.x) * (B.y - O.y) - (A.y - O.y) * (B.x - O.x);
}

vector <Point> convex_hull(vector <Point> &P) {
  int n = P.size(), k = 0;
  vector <Point> H(2*n);
  sort(P.begin(), P.end());
  for(int i=0; i<n; i++) {
    while(k >= 2 && cross(H[k-2], H[k-1], P[i]) <= 0) k--;
    H[k++] = P[i];
  }
  for(int i=n-2, t = k+1; i>=0; i--) {
    while(k >= t && cross(H[k-2], H[k-1], P[i]) <= 0) k--;
    H[k++] = P[i];
  }
  H.resize(k-1);
  return H;
}

int main() {
  int n;
  cin >> n;
  long long x, y;
  vector <Point> v;
  for(int i=0; i<n; i++) {
    cin >> x >> y;
    v.push_back(Point(x,y));
  }
  if(n < 4) {
    cout << "NO" << endl;
    return 0;
  }
  vector <Point> h = convex_hull(v);
  if(h.size() >= 4) {
    cout << "YES" << endl;
    for(int i=0; i<4; i++) {
      cout << h[i].x << " " << h[i].y << endl;
    }
    return 0;
  }
  if(n == 4) {
    cout << "NO" << endl;
    return 0;
  }
  auto isin = [&] (Point r) -> bool {
    for(int i=0; i<h.size(); i++) {
      if(h[i].x == r.x && h[i].y == r.y) return true;
    }
    return false;
  };
  vector <Point> tmp;
  for(int i=0; i<5 && tmp.size() < 2; i++) {
    if(isin(v[i])) continue;
    tmp.push_back(v[i]);
  }
  vector <Point> t1 = {h[0], h[1], tmp[0], tmp[1]};
  vector <Point> t2 = {h[0], h[2], tmp[0], tmp[1]};
  vector <Point> t3 = {h[2], h[1], tmp[0], tmp[1]};
  t1 = convex_hull(t1);
  t2 = convex_hull(t2);
  t3 = convex_hull(t3);
  if(t1.size() == 4) {
    cout << "YES" << endl;
    for(int i=0; i<4; i++) {
      cout << t1[i].x << " " << t1[i].y << endl;
    }
    return 0;
  }
  t1 = t2;
  if(t1.size() == 4) {
    cout << "YES" << endl;
    for(int i=0; i<4; i++) {
      cout << t1[i].x << " " << t1[i].y << endl;
    }
    return 0;
  }
  t1 = t3;
  if(t1.size() == 4) {
    cout << "YES" << endl;
    for(int i=0; i<4; i++) {
      cout << t1[i].x << " " << t1[i].y << endl;
    }
    return 0;
  }
  assert(0);
  cout << "NO" << endl;
  return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

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: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED