Problem p02926 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma GCC optimize("O3")
#pragma GCC target("sse4")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T>
using Tree =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 100001; // check the limits, dummy

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int N;
  cin >> N;

  ll data[N][2];
  F0R(i, N) { F0R(j, 2) cin >> data[i][j]; }

  ll ans = 0;

  F0R(xP, 2) {
    F0R(yP, 2) {
      ll xC = xP;
      if (xC == 0)
        xC = -1;
      ll yC = yP;
      if (yP == 0)
        yC = -1;

      vpl oldPoints;
      oldPoints.pb({0, 0});

      F0R(i, N) {
        vpl newPoints;
        F0R(j, sz(oldPoints)) {
          newPoints.pb(oldPoints[j]);
          newPoints.pb(mp(oldPoints[j].f + data[i][0] * xC,
                          oldPoints[j].s + data[i][1] * yC));
        }
        oldPoints.clear();

        F0R(x, sz(newPoints)) {
          int k = sz(oldPoints) - 1;
          if (sz(oldPoints) == 0 || oldPoints[k].f < newPoints[x].f ||
              oldPoints[k].s < newPoints[x].s) {
            oldPoints.pb(newPoints[x]);
          }
        }
      }

      F0R(i, sz(oldPoints)) {
        ans = max(ans, oldPoints[i].f * oldPoints[i].f +
                           oldPoints[i].s * oldPoints[i].s);
      }
    }
  }

  cout << setprecision(30) << sqrtl((ld)ans) << endl;

  return 0;
}

Fixed submission:
#pragma GCC optimize("O3")
#pragma GCC target("sse4")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T>
using Tree =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 100001; // check the limits, dummy

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int N;
  cin >> N;

  ll data[N][2];
  F0R(i, N) { F0R(j, 2) cin >> data[i][j]; }

  ll ans = 0;

  F0R(xP, 2) {
    F0R(yP, 2) {
      ll xC = xP;
      if (xC == 0)
        xC = -1;
      ll yC = yP;
      if (yP == 0)
        yC = -1;

      vpl oldPoints;
      oldPoints.pb({0, 0});

      F0R(i, N) {
        vpl newPoints;
        F0R(j, sz(oldPoints)) {
          newPoints.pb(oldPoints[j]);
          newPoints.pb(mp(oldPoints[j].f + data[i][0] * xC,
                          oldPoints[j].s + data[i][1] * yC));
        }
        sort(all(newPoints));
        reverse(all(newPoints));
        oldPoints.clear();

        F0R(x, sz(newPoints)) {
          int k = sz(oldPoints) - 1;
          if (sz(oldPoints) == 0 || oldPoints[k].f < newPoints[x].f ||
              oldPoints[k].s < newPoints[x].s) {
            oldPoints.pb(newPoints[x]);
          }
        }
      }

      F0R(i, sz(oldPoints)) {
        ans = max(ans, oldPoints[i].f * oldPoints[i].f +
                           oldPoints[i].s * oldPoints[i].s);
      }
    }
  }

  cout << setprecision(30) << sqrtl((ld)ans) << endl;

  return 0;
}