Problem p02616 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
const long long INF = 1LL << 60;
const long long MOD = 1000000007;
const double PI = acos(-1.0);
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = (n - 1); i >= 0; --i)
#define perm(c)                                                                \\
  sort(ALL(c));                                                                \\
  for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define to_s to_string
#define len(v) (ll) v.size()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define print(x) cout << (x) << '\\n'
#define drop(x) cout << (x) << '\\n', exit(0)
#define debug(x) cout << #x << ": " << (x) << '\\n'
using namespace std;
using ll = long long;
typedef pair<ll, ll> P;
typedef vector<ll> vec;
typedef vector<vector<ll>> vec2;
typedef vector<vector<vector<ll>>> vec3;
template <class S, class T> inline bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class S, class T> inline bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
inline ll msb(ll v) { return 1 << (31 - __builtin_clzll(v)); }
inline ll devc(ll x, ll y) { return (x + y - 1) / y; }
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a * (b / gcd(a, b)); }

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3> &t) {
  os << get<0>(t) << " " << get<1>(t) << " " << get<2>(t);
  return os;
}

template <typename T1, typename T2, typename T3>
istream &operator>>(istream &is, tuple<T1, T2, T3> &t) {
  is >> get<0>(t) >> get<1>(t) >> get<2>(t);
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); ++i) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const set<T> &st) {
  int ct = 0;
  for (auto &s : st)
    cout << s << (++ct != st.size() ? " " : "");
  return os;
}

/*---------------------------------    Tools
 * ------------------------------------------*/
template <typename T> vector<T> cumsum(const vector<T> &X) {
  vector<T> res(X.size() + 1, 0);
  for (int i = 0; i < X.size(); ++i)
    res[i + 1] += res[i] + X[i];
  return res;
}

template <typename S, typename T, typename F>
pair<T, T> bisearch(S left, T right, F f) {
  while (abs(right - left) > 1) {
    T mid = (right + left) / 2;
    if (f(mid))
      right = mid;
    else
      left = mid;
  }
  return {left, right};
}

template <typename S, typename T, typename F>
double trisearch(S left, T right, F f, int maxLoop = 90) {
  double low = left, high = right;
  while (maxLoop--) {
    double mid_left = high / 3 + low * 2 / 3;
    double mid_right = high * 2 / 3 + low / 3;
    if (f(mid_left) >= f(mid_right))
      low = mid_left;
    else
      high = mid_right;
  }
  return (low + high) * 0.5;
}

template <typename F> ll ternarySearch(ll L, ll R, F f) { //[L, R)
  ll lo = L - 1, hi = R - 1;
  while (lo + 1 != hi) {
    ll mi = (lo + hi) / 2;
    if (f(mi) <= f(mi + 1))
      hi = mi;
    else
      lo = mi;
  }
  return hi;
}

template <int MOD> struct modint {
  ll val;
  constexpr modint(ll v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr modint operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr modint operator+(const modint &r) const noexcept {
    return modint(*this) += r;
  }
  constexpr modint operator-(const modint &r) const noexcept {
    return modint(*this) -= r;
  }
  constexpr modint operator*(const modint &r) const noexcept {
    return modint(*this) *= r;
  }
  constexpr modint operator/(const modint &r) const noexcept {
    return modint(*this) /= r;
  }
  constexpr modint &operator++() noexcept {
    val += 1;
    return *this;
  }
  constexpr modint &operator--() noexcept {
    val -= 1;
    return *this;
  }
  constexpr modint &operator+=(const modint &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr modint &operator-=(const modint &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr modint &operator*=(const modint &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr modint &operator/=(const modint &r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const modint &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const modint &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr istream &operator>>(istream &is, modint<MOD> &x) noexcept {
    is >> x.val;
    x += 0;
    return is;
  }
  friend constexpr ostream &operator<<(ostream &os,
                                       const modint<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr modint<MOD> modpow(const modint<MOD> &a,
                                      long long n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};
using mint = modint<MOD>;

/*------------------------------- Main Code Here
 * -----------------------------------------*/

int main() {
  ll N, K;
  cin >> N >> K;
  vec A(N);
  cin >> A;
  sort(RALL(A));
  bool flag = true;
  for (auto a : A)
    if (a >= 0)
      flag = false;

  if (K == N) {
    mint ans = 1;
    for (auto a : A)
      ans *= a;
    drop(ans);
  }

  if ((K % 2 == 1) and flag) {
    mint ans = 1;
    rep(i, K) ans *= A[i];
    drop(ans);
  }

  priority_queue<ll> pos, neg;
  for (auto a : A)
    (a >= 0 ? pos : neg).push(abs(a));

  mint ans = 1;
  ll ct = 0;
  while (!pos.empty() or !neg.empty()) {
    if (ct == K)
      break;

    if (pos.empty()) {
      ct += 2;
      ans *= neg.top();
      neg.pop();
      ans *= neg.top();
      neg.pop();
      continue;
    }

    if ((len(neg) <= 1) or (ct == K - 1)) {
      ++ct;
      ans *= pos.top();
      pos.pop();
      continue;
    }

    ll p1 = pos.top();
    pos.pop();
    ll pm = p1;
    if (!pos.empty())
      pm *= pos.top();
    pos.push(p1);

    ll m1 = neg.top();
    neg.pop();
    ll mm = m1 * neg.top();
    neg.push(m1);

    if (pm >= mm) {
      ++ct;
      ans *= p1;
      pos.pop();
      continue;
    }
    ct += 2;
    ans *= mm;
    neg.pop();
    neg.pop();
  }

  print(ans);

  return 0;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
const long long INF = 1LL << 60;
const long long MOD = 1000000007;
const double PI = acos(-1.0);
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = (n - 1); i >= 0; --i)
#define perm(c)                                                                \\
  sort(ALL(c));                                                                \\
  for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define to_s to_string
#define len(v) (ll) v.size()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define print(x) cout << (x) << '\\n'
#define drop(x) cout << (x) << '\\n', exit(0)
#define debug(x) cout << #x << ": " << (x) << '\\n'
using namespace std;
using ll = long long;
typedef pair<ll, ll> P;
typedef vector<ll> vec;
typedef vector<vector<ll>> vec2;
typedef vector<vector<vector<ll>>> vec3;
template <class S, class T> inline bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class S, class T> inline bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
inline ll msb(ll v) { return 1 << (31 - __builtin_clzll(v)); }
inline ll devc(ll x, ll y) { return (x + y - 1) / y; }
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a * (b / gcd(a, b)); }

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T1, typename T2, typename T3>
ostream &operator<<(ostream &os, const tuple<T1, T2, T3> &t) {
  os << get<0>(t) << " " << get<1>(t) << " " << get<2>(t);
  return os;
}

template <typename T1, typename T2, typename T3>
istream &operator>>(istream &is, tuple<T1, T2, T3> &t) {
  is >> get<0>(t) >> get<1>(t) >> get<2>(t);
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); ++i) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const set<T> &st) {
  int ct = 0;
  for (auto &s : st)
    cout << s << (++ct != st.size() ? " " : "");
  return os;
}

/*---------------------------------    Tools
 * ------------------------------------------*/
template <typename T> vector<T> cumsum(const vector<T> &X) {
  vector<T> res(X.size() + 1, 0);
  for (int i = 0; i < X.size(); ++i)
    res[i + 1] += res[i] + X[i];
  return res;
}

template <typename S, typename T, typename F>
pair<T, T> bisearch(S left, T right, F f) {
  while (abs(right - left) > 1) {
    T mid = (right + left) / 2;
    if (f(mid))
      right = mid;
    else
      left = mid;
  }
  return {left, right};
}

template <typename S, typename T, typename F>
double trisearch(S left, T right, F f, int maxLoop = 90) {
  double low = left, high = right;
  while (maxLoop--) {
    double mid_left = high / 3 + low * 2 / 3;
    double mid_right = high * 2 / 3 + low / 3;
    if (f(mid_left) >= f(mid_right))
      low = mid_left;
    else
      high = mid_right;
  }
  return (low + high) * 0.5;
}

template <typename F> ll ternarySearch(ll L, ll R, F f) { //[L, R)
  ll lo = L - 1, hi = R - 1;
  while (lo + 1 != hi) {
    ll mi = (lo + hi) / 2;
    if (f(mi) <= f(mi + 1))
      hi = mi;
    else
      lo = mi;
  }
  return hi;
}

template <int MOD> struct modint {
  ll val;
  constexpr modint(ll v = 0) noexcept : val(v % MOD) {
    if (val < 0)
      val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr modint operator-() const noexcept { return val ? MOD - val : 0; }
  constexpr modint operator+(const modint &r) const noexcept {
    return modint(*this) += r;
  }
  constexpr modint operator-(const modint &r) const noexcept {
    return modint(*this) -= r;
  }
  constexpr modint operator*(const modint &r) const noexcept {
    return modint(*this) *= r;
  }
  constexpr modint operator/(const modint &r) const noexcept {
    return modint(*this) /= r;
  }
  constexpr modint &operator++() noexcept {
    val += 1;
    return *this;
  }
  constexpr modint &operator--() noexcept {
    val -= 1;
    return *this;
  }
  constexpr modint &operator+=(const modint &r) noexcept {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }
  constexpr modint &operator-=(const modint &r) noexcept {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr modint &operator*=(const modint &r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr modint &operator/=(const modint &r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }
  constexpr bool operator==(const modint &r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator!=(const modint &r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr istream &operator>>(istream &is, modint<MOD> &x) noexcept {
    is >> x.val;
    x += 0;
    return is;
  }
  friend constexpr ostream &operator<<(ostream &os,
                                       const modint<MOD> &x) noexcept {
    return os << x.val;
  }
  friend constexpr modint<MOD> modpow(const modint<MOD> &a,
                                      long long n) noexcept {
    if (n == 0)
      return 1;
    auto t = modpow(a, n / 2);
    t = t * t;
    if (n & 1)
      t = t * a;
    return t;
  }
};
using mint = modint<MOD>;

/*------------------------------- Main Code Here
 * -----------------------------------------*/

int main() {
  ll N, K;
  cin >> N >> K;
  vec A(N);
  cin >> A;
  sort(RALL(A));
  bool flag = true;
  for (auto a : A)
    if (a >= 0)
      flag = false;

  if ((K % 2 == 1) and flag) {
    mint ans = 1;
    rep(i, K) ans *= A[i];
    drop(ans);
  }

  priority_queue<ll> pos, neg;
  for (auto a : A)
    (a >= 0 ? pos : neg).push(abs(a));

  mint ans = 1;
  ll ct = 0;
  while (!pos.empty() or !neg.empty()) {
    if (ct == K)
      break;

    if (pos.empty()) {
      ct += 2;
      ans *= neg.top();
      neg.pop();
      ans *= neg.top();
      neg.pop();
      continue;
    }

    if (len(neg) <= 1 or ct == K - 1) {
      ++ct;
      ans *= pos.top();
      pos.pop();
      continue;
    }

    ll p1 = pos.top();
    pos.pop();
    ll pm = p1;
    if (!pos.empty())
      pm *= pos.top();
    pos.push(p1);

    ll m1 = neg.top();
    neg.pop();
    ll m2 = neg.top();
    neg.push(m1);

    if (pm >= m1 * m2) {
      ++ct;
      ans *= p1;
      pos.pop();
      continue;
    }
    ct += 2;
    ans *= m1 * m2;
    neg.pop();
    neg.pop();
  }

  print(ans);

  return 0;
}