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

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

typedef long long ll;
#define pa pair<int, int>
#define pal pair<long long, long long>
#define pali pair<long long, int>
#define pad pair<double, double>
#define pb push_back
#define mp make_pair
#define COUT(v)                                                                \\
  for (int64_t i = 0; i < (v).size(); ++i) {                                   \\
    cout << v.at(i) << endl;                                                   \\
  }
#define REP(i, n) for (int64_t i = 0; i < n; ++i)
#define FOR(i, r, n) for (int64_t i = (r); i < n; ++i)
#define VIN(v)                                                                 \\
  for (int64_t i = 0; i < (v).size(); ++i) {                                   \\
    cin >> (v).at(i);                                                          \\
  }

typedef vector<bool> bvec;
typedef vector<int> ivec;
typedef vector<long long> lvec;
typedef vector<double> dvec;
typedef vector<pa> pavec;
typedef vector<vector<pa>> pamat;
typedef vector<pali> palivec;
typedef vector<pal> palvec;

typedef vector<vector<bool>> bmat;
typedef vector<vector<int>> imat;
typedef vector<vector<long long>> lmat;

typedef vector<string> svec;
typedef vector<vector<string>> smat;
const ll infll = (1LL << 60) - 1;
const int inf = (1 << 30) - 1;
const ll MOD = 1000000007;

ll gcd(ll x, ll y) {
  ll r = x % y;
  if (r == 0)
    return y;
  else
    return gcd(y, r);
}

ll lcm(ll x, ll y) { return x * y / gcd(x, y); }

lvec mfactor(ll n) {
  bvec ip(n, true);
  lvec mf(n, -1);
  ip[0] = false;
  ip[1] = false;
  mf[0] = 0;
  mf[1] = 1;
  REP(i, n) {
    if (ip[i]) {
      mf[i] = i;
      for (ll j = i * i; j < n; j += i) {
        ip[j] = false;
        if (mf[j] == -1)
          mf[j] = i;
      }
    }
  }
  return mf;
}

palivec get_prime(ll n, const lvec &mf) {
  palivec plist;
  while (n != 1) {
    int cnt = 0;
    ll m = mf[n];
    while (mf[n] == m) {
      cnt++;
      n /= m;
    }
    plist.pb(pali(m, cnt));
  }
  return plist;
}

void COMinit(int m, lvec &fac, lvec &finv) {
  lvec inv(m);
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < m; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}

ll pow_mod(ll a, ll n) {
  ll x = 1;
  while (n > 0) {
    if (n & 1) {
      x = x * a % MOD;
    }
    a = a * a % MOD;
    n >>= 1;
  }
  return x;
}

ll COM(int n, int k, const lvec &fac, const lvec &finv) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return (fac[n] * (finv[k] * finv[n - k] % MOD)) % MOD;
}

ll modinv(ll a, ll m) {
  ll b = m, u = 1, v = 0;
  while (b) {
    ll t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}

typedef map<ll, double> Prob;

void calc(Prob &firsts, Prob &seconds, Prob &thirds) {
  vector<pair<double, lvec>> pr;
  for (auto fv : firsts) {
    for (auto sv : seconds) {
      for (auto tv : thirds) {
        if (fv.first == sv.first || sv.first == tv.first ||
            fv.first == tv.first)
          continue;
        lvec s(3);
        s[0] = (fv.first);
        s[1] = (sv.first);
        s[2] = (tv.first);
        double p = fv.second * sv.second * tv.second;
        pr.pb(pair<double, lvec>(p, s));
      }
    }
  }

  sort(pr.begin(), pr.end(), greater<pair<double, lvec>>());
  for (auto v : pr) {
    cout << "prob: " << v.first << " : odds : " << 1 / v.first << " : ";
    for (auto vv : v.second) {
      cout << vv << ' ';
    }
    cout << endl;
  }
}

ll cnt(ll x) {
  ll s = 0;
  ll k = 26;
  for (int i = 0; i < x; i++) {
    s = s + k;
    k *= 26;
  }
  return s;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, k;
  cin >> n >> k;

  lvec p;
  lvec m;
  for (ll i = 0; i < n; i++) {
    ll a;
    cin >> a;
    if (a >= 0)
      p.pb(a);
    else
      m.pb(a);
  }
  sort(p.rbegin(), p.rend());
  sort(m.begin(), m.end());
  ll nm = m.size(), np = p.size();

  if (n == k) {
    ll ans = 1;
    for (ll v : p) {
      ans *= v;
      ans %= MOD;
    }
    for (ll v : m) {
      ans *= MOD + v;
      ans %= MOD;
    }
    cout << ans << endl;
    return 0;
  }

  if (np == 0 && k % 2) {
    ll ans = 1;
    for (ll i = nm - 1; i >= nm - k; i--) {
      ans *= (MOD + m[i]);
      ans %= MOD;
    }
    cout << ans << endl;
    return 0;
  }

  ll ip = 0, im = 0;
  ll ans = 1;
  if (k % 2) {
    ans = p[0];
    ++ip;
    --k;
  }
  while (k > 0) {
    if (im > (nm - 2)) {
      for (ll i = ip; i < ip + k; i++) {
        ans *= p[i];
        ans %= MOD;
      }
      break;
    }
    if (ip > (np - 2)) {
      for (ll i = im; i < im + k; i++) {
        ans *= m[i];
        ans %= MOD;
      }
      break;
    }
    ll pp = p[ip] * p[ip + 1];
    ll pm = m[im] * m[im + 1];
    // cout << pp << ' ' << pm << endl;
    if (pp > pm) {
      ans *= pp % MOD;
      ans %= MOD;
      ip += 2;
    } else {
      ans *= pm % MOD;
      ans %= MOD;
      im += 2;
    }
    k -= 2;
  }
  cout << ans << endl;
}


Error: 0

Fixed submission:

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

typedef long long ll;
#define pa pair<int, int>
#define pal pair<long long, long long>
#define pali pair<long long, int>
#define pad pair<double, double>
#define pb push_back
#define mp make_pair
#define COUT(v)                                                                \\
  for (int64_t i = 0; i < (v).size(); ++i) {                                   \\
    cout << v.at(i) << endl;                                                   \\
  }
#define REP(i, n) for (int64_t i = 0; i < n; ++i)
#define FOR(i, r, n) for (int64_t i = (r); i < n; ++i)
#define VIN(v)                                                                 \\
  for (int64_t i = 0; i < (v).size(); ++i) {                                   \\
    cin >> (v).at(i);                                                          \\
  }

typedef vector<bool> bvec;
typedef vector<int> ivec;
typedef vector<long long> lvec;
typedef vector<double> dvec;
typedef vector<pa> pavec;
typedef vector<vector<pa>> pamat;
typedef vector<pali> palivec;
typedef vector<pal> palvec;

typedef vector<vector<bool>> bmat;
typedef vector<vector<int>> imat;
typedef vector<vector<long long>> lmat;

typedef vector<string> svec;
typedef vector<vector<string>> smat;
const ll infll = (1LL << 60) - 1;
const int inf = (1 << 30) - 1;
const ll MOD = 1000000007;

ll gcd(ll x, ll y) {
  ll r = x % y;
  if (r == 0)
    return y;
  else
    return gcd(y, r);
}

ll lcm(ll x, ll y) { return x * y / gcd(x, y); }

lvec mfactor(ll n) {
  bvec ip(n, true);
  lvec mf(n, -1);
  ip[0] = false;
  ip[1] = false;
  mf[0] = 0;
  mf[1] = 1;
  REP(i, n) {
    if (ip[i]) {
      mf[i] = i;
      for (ll j = i * i; j < n; j += i) {
        ip[j] = false;
        if (mf[j] == -1)
          mf[j] = i;
      }
    }
  }
  return mf;
}

palivec get_prime(ll n, const lvec &mf) {
  palivec plist;
  while (n != 1) {
    int cnt = 0;
    ll m = mf[n];
    while (mf[n] == m) {
      cnt++;
      n /= m;
    }
    plist.pb(pali(m, cnt));
  }
  return plist;
}

void COMinit(int m, lvec &fac, lvec &finv) {
  lvec inv(m);
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < m; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}

ll pow_mod(ll a, ll n) {
  ll x = 1;
  while (n > 0) {
    if (n & 1) {
      x = x * a % MOD;
    }
    a = a * a % MOD;
    n >>= 1;
  }
  return x;
}

ll COM(int n, int k, const lvec &fac, const lvec &finv) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return (fac[n] * (finv[k] * finv[n - k] % MOD)) % MOD;
}

ll modinv(ll a, ll m) {
  ll b = m, u = 1, v = 0;
  while (b) {
    ll t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  u %= m;
  if (u < 0)
    u += m;
  return u;
}

typedef map<ll, double> Prob;

void calc(Prob &firsts, Prob &seconds, Prob &thirds) {
  vector<pair<double, lvec>> pr;
  for (auto fv : firsts) {
    for (auto sv : seconds) {
      for (auto tv : thirds) {
        if (fv.first == sv.first || sv.first == tv.first ||
            fv.first == tv.first)
          continue;
        lvec s(3);
        s[0] = (fv.first);
        s[1] = (sv.first);
        s[2] = (tv.first);
        double p = fv.second * sv.second * tv.second;
        pr.pb(pair<double, lvec>(p, s));
      }
    }
  }

  sort(pr.begin(), pr.end(), greater<pair<double, lvec>>());
  for (auto v : pr) {
    cout << "prob: " << v.first << " : odds : " << 1 / v.first << " : ";
    for (auto vv : v.second) {
      cout << vv << ' ';
    }
    cout << endl;
  }
}

ll cnt(ll x) {
  ll s = 0;
  ll k = 26;
  for (int i = 0; i < x; i++) {
    s = s + k;
    k *= 26;
  }
  return s;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, k;
  cin >> n >> k;
  lvec ab(n);
  lvec p;
  lvec m;
  for (int i = 0; i < n; i++) {
    ll a;
    cin >> a;
    if (a >= 0)
      p.pb(a);
    else
      m.pb(a);
    ab[i] = abs(a);
  }
  sort(ab.begin(), ab.end());
  sort(p.rbegin(), p.rend());
  sort(m.begin(), m.end());
  if (p.size() == 0 && k % 2) {
    ll ans = 1;
    for (int i = m.size() - 1; i >= m.size() - k; i--) {
      if (m[i] < 0) {
        m[i] = MOD + m[i];
      }
      ans *= m[i];
      ans %= MOD;
    }
    cout << ans << endl;
    return 0;
  }

  ll ip = 0, im = 0;
  ll ans = 1;
  if (k % 2) {
    ans = p[0];
    --k;
  }

  while (k > 0) {
    if (im + 1 > (int)m.size() - 1) {
      for (int i = ip; i < ip + k; i++) {
        ans *= p[i];
        ans %= MOD;
      }
      break;
    } else if (ip + 1 > (int)m.size() - 1) {

      for (int i = im; i < im + k; i++) {
        ans *= m[i];
        ans %= MOD;
      }
      break;
    } else {

      ll pp = p[ip] * p[ip + 1];
      ll pm = m[im] * m[im + 1];
      // cout << pp << ' ' << pm << endl;
      if (pp > pm) {
        ans *= pp % MOD;
        ans %= MOD;
        ip += 2;
      } else {
        ans *= pm % MOD;
        ans %= MOD;
        ip += 1;
      }
    }
    k -= 2;
  }
  cout << ans << endl;
}