Problem p02616 (C++) — buggy submission, verdict: Runtime Error

#pragma GCC optimize("O3")
#pragma GCC target("sse4")

#include <bits/stdc++.h>

using namespace std;

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;

#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 trav(a, x) for (auto &a : x)

#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()
#define ins insert

template <class T> bool ckmin(T &a, const T &b) { return b < a ? a = b, 1 : 0; }
template <class T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }

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

const int MOD = 1000000007;
const char nl = '\\n';
const int MX = 100001; // check the limits, dummy

struct mi {
  ll v;
  explicit operator ll() const { return v; }
  mi() { v = 0; }
  mi(ll _v) {
    v = (-MOD < _v && _v < MOD) ? _v : _v % MOD;
    if (v < 0)
      v += MOD;
  }
  friend bool operator==(const mi &a, const mi &b) { return a.v == b.v; }
  friend bool operator!=(const mi &a, const mi &b) { return !(a == b); }
  friend bool operator<(const mi &a, const mi &b) { return a.v < b.v; }

  mi &operator+=(const mi &m) {
    if ((v += m.v) >= MOD)
      v -= MOD;
    return *this;
  }
  mi &operator-=(const mi &m) {
    if ((v -= m.v) < 0)
      v += MOD;
    return *this;
  }
  mi &operator*=(const mi &m) {
    v = v * m.v % MOD;
    return *this;
  }
  mi &operator/=(const mi &m) { return (*this) *= inv(m); }
  friend mi pow(mi a, ll p) {
    mi ans = 1;
    assert(p >= 0);
    for (; p; p /= 2, a *= a)
      if (p & 1)
        ans *= a;
    return ans;
  }
  friend mi inv(const mi &a) {
    assert(a.v != 0);
    return pow(a, MOD - 2);
  }

  mi operator-() const { return mi(-v); }
  mi &operator++() { return *this += 1; }
  mi &operator--() { return *this -= 1; }
  mi operator++(int) {
    mi temp;
    temp.v = v++;
    return temp;
  }
  mi operator--(int) {
    mi temp;
    temp.v = v--;
    return temp;
  }
  friend mi operator+(mi a, const mi &b) { return a += b; }
  friend mi operator-(mi a, const mi &b) { return a -= b; }
  friend mi operator*(mi a, const mi &b) { return a *= b; }
  friend mi operator/(mi a, const mi &b) { return a /= b; }
  friend ostream &operator<<(ostream &os, const mi &m) {
    os << m.v;
    return os;
  }
  friend istream &operator>>(istream &is, mi &m) {
    ll x;
    is >> x;
    m.v = x;
    return is;
  }
};

typedef vector<mi> vmi;
typedef pair<mi, mi> pmi;
typedef vector<pmi> vpmi;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int N, K;
  cin >> N >> K;
  vl pos, neg;
  bool zero = false;
  F0R(i, N) {
    ll cur;
    cin >> cur;
    if (cur > 0) {
      pos.pb(cur);
    } else if (cur < 0) {
      neg.pb(cur);
    } else
      zero = true;
  }

  if (!zero && ((N == K && sz(neg) % 2) || (sz(pos) == 0 && K % 2))) {
    mi ans = 1;
    vl ops = pos;
    F0R(i, sz(neg)) ops.pb(-neg[i]);
    sort(all(ops));
    F0R(i, K) ans *= ops[i];
    cout << -ans << nl;
    return 0;
  }

  sort(all(pos));
  sort(all(neg));
  reverse(all(pos));
  mi pp[sz(pos) + 1], pn[sz(neg) + 1];
  pp[0] = 1;
  F0R(i, sz(pos)) { pp[i + 1] = pp[i] * pos[i]; }
  pn[0] = 1;
  F0R(i, sz(neg)) { pn[i + 1] = pn[i] * neg[i]; }
  mi ans = 1;
  bool found = false;
  FOR(i, max(K - sz(neg), 0), min(K, sz(pos)) + 1) {
    if ((K - i) % 2)
      continue;
    if (found && (pos[i - 1] * pos[i - 2] < neg[K - i + 1] * neg[K - i]))
      break;
    ans = pp[i] * pn[K - i];
    found = true;
  }

  if (!found) {
    cout << 0 << nl;
    return 0;
  }
  cout << ans << nl;

  return 0;
}

// read the question correctly (ll vs int)
// template by bqi343


Error: 0

Fixed submission:

#pragma GCC optimize("O3")
#pragma GCC target("sse4")

#include <bits/stdc++.h>

using namespace std;

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;

#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 trav(a, x) for (auto &a : x)

#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()
#define ins insert

template <class T> bool ckmin(T &a, const T &b) { return b < a ? a = b, 1 : 0; }
template <class T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }

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

const int MOD = 1000000007;
const char nl = '\\n';
const int MX = 100001; // check the limits, dummy

struct mi {
  ll v;
  explicit operator ll() const { return v; }
  mi() { v = 0; }
  mi(ll _v) {
    v = (-MOD < _v && _v < MOD) ? _v : _v % MOD;
    if (v < 0)
      v += MOD;
  }
  friend bool operator==(const mi &a, const mi &b) { return a.v == b.v; }
  friend bool operator!=(const mi &a, const mi &b) { return !(a == b); }
  friend bool operator<(const mi &a, const mi &b) { return a.v < b.v; }

  mi &operator+=(const mi &m) {
    if ((v += m.v) >= MOD)
      v -= MOD;
    return *this;
  }
  mi &operator-=(const mi &m) {
    if ((v -= m.v) < 0)
      v += MOD;
    return *this;
  }
  mi &operator*=(const mi &m) {
    v = v * m.v % MOD;
    return *this;
  }
  mi &operator/=(const mi &m) { return (*this) *= inv(m); }
  friend mi pow(mi a, ll p) {
    mi ans = 1;
    assert(p >= 0);
    for (; p; p /= 2, a *= a)
      if (p & 1)
        ans *= a;
    return ans;
  }
  friend mi inv(const mi &a) {
    assert(a.v != 0);
    return pow(a, MOD - 2);
  }

  mi operator-() const { return mi(-v); }
  mi &operator++() { return *this += 1; }
  mi &operator--() { return *this -= 1; }
  mi operator++(int) {
    mi temp;
    temp.v = v++;
    return temp;
  }
  mi operator--(int) {
    mi temp;
    temp.v = v--;
    return temp;
  }
  friend mi operator+(mi a, const mi &b) { return a += b; }
  friend mi operator-(mi a, const mi &b) { return a -= b; }
  friend mi operator*(mi a, const mi &b) { return a *= b; }
  friend mi operator/(mi a, const mi &b) { return a /= b; }
  friend ostream &operator<<(ostream &os, const mi &m) {
    os << m.v;
    return os;
  }
  friend istream &operator>>(istream &is, mi &m) {
    ll x;
    is >> x;
    m.v = x;
    return is;
  }
};

typedef vector<mi> vmi;
typedef pair<mi, mi> pmi;
typedef vector<pmi> vpmi;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int N, K;
  cin >> N >> K;
  vl pos, neg;
  bool zero = false;
  F0R(i, N) {
    ll cur;
    cin >> cur;
    if (cur > 0) {
      pos.pb(cur);
    } else if (cur < 0) {
      neg.pb(cur);
    } else
      zero = true;
  }

  if (!zero && ((N == K && sz(neg) % 2) || (sz(pos) == 0 && K % 2))) {
    mi ans = 1;
    vl ops = pos;
    F0R(i, sz(neg)) ops.pb(-neg[i]);
    sort(all(ops));
    F0R(i, K) ans *= ops[i];
    cout << -ans << nl;
    return 0;
  }

  if (sz(pos) + sz(neg) - (sz(neg) % 2) < K) {
    cout << 0 << nl;
    return 0;
  }

  sort(all(pos));
  sort(all(neg));
  reverse(all(pos));
  mi pp[sz(pos) + 1], pn[sz(neg) + 1];
  pp[0] = 1;
  F0R(i, sz(pos)) { pp[i + 1] = pp[i] * pos[i]; }
  pn[0] = 1;
  F0R(i, sz(neg)) { pn[i + 1] = pn[i] * neg[i]; }
  mi ans = 1;
  bool found = false;
  F0R(i, sz(pos) + 1) {
    if ((K - i) % 2)
      continue;
    if (K - i > sz(neg))
      continue;
    if (found && (pos[i - 1] * pos[i - 2] < neg[K - i + 1] * neg[K - i]))
      break;
    ans = pp[i] * pn[K - i];
    found = true;
  }

  cout << ans << nl;

  return 0;
}

// read the question correctly (ll vs int)
// template by bqi343