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

#include <algorithm>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

#define MOD 1000000007
#define MOD2 998244353
#define int long long
#define double long double
#define EPS 1e-9
// #define PI 3.14159265358979

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;

template <typename T> ostream &operator<<(ostream &os, const vector<T> &A) {
  for (int i = 0; i < A.size(); i++)
    os << A[i] << " ";
  os << endl;
  return os;
}
template <> ostream &operator<<(ostream &os, const vector<vector<int>> &A) {
  int N = A.size();
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < A[i].size(); j++)
      os << A[i][j] << " ";
    os << endl;
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}

typedef pair<int, int> pii;
typedef long long ll;

struct edge {
  int from, to, d, c, i;
  edge(int _from = 0, int _to = 0, int _d = 0, int _c = 0) {
    from = _from;
    to = _to;
    d = _d;
    c = _c;
  }
  bool operator<(const edge &rhs) const {
    return (d == rhs.d) ? (c < rhs.c) : (d < rhs.d);
  }
};
struct aabb {
  int x1, y1, x2, y2;
  aabb(int x1, int y1, int x2, int y2) : x1(x1), y1(y1), x2(x2), y2(y2) {}
};

typedef vector<edge> edges;
typedef vector<edges> graph;
struct flow {
  int to, cap, rev, cost;
  flow(int to = 0, int cap = 0, int rev = 0, int cost = 0)
      : to(to), cap(cap), rev(rev), cost(cost) {}
};
typedef vector<vector<flow>> flows;

const int di[4] = {0, -1, 0, 1};
const int dj[4] = {-1, 0, 1, 0};
const int ci[5] = {0, 0, -1, 0, 1};
const int cj[5] = {0, -1, 0, 1, 0};
const ll LINF = LLONG_MAX / 2;
const int INF = INT_MAX / 2;
const double PI = acos(-1);

int pow2(int n) { return 1LL << n; }
template <typename T, typename U> bool chmin(T &x, const U &y) {
  if (x > y) {
    x = y;
    return true;
  }
  return false;
}
template <typename T, typename U> bool chmax(T &x, const U &y) {
  if (x < y) {
    x = y;
    return true;
  }
  return false;
}

template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  fill((T *)array, (T *)(array + N), val);
}
struct initializer {
  initializer() { cout << fixed << setprecision(20); }
};
initializer _____;

int N, M, K, T, Q, H, W;
signed main() {
  cin >> N >> K;
  vector<int> A(N);
  rep(i, N) cin >> A[i];
  int ans = 1;
  if (N == K) {
    rep(i, N)(ans *= A[i]) %= MOD;
    ans += MOD;
    (ans %= MOD);
    cout << ans << endl;
    return 0;
  }
  vector<int> pos, neg;
  rep(i, N) {
    if (A[i] < 0)
      neg.push_back(-A[i]);
    else
      pos.push_back(A[i]);
  }
  if (pos.size() == 0 && (K & 1)) {
    sort(neg.begin(), neg.end());
    rep(i, K)(ans *= neg[i]) %= MOD;
    ans = -ans;
    ans %= MOD;
    ans = (ans + MOD) % MOD;
    cout << ans << endl;
    return 0;
  }
  sort(pos.rbegin(), pos.rend());
  sort(neg.rbegin(), neg.rend());
  vector<int> vans;
  int i = 0, j = 0;
  if (K & 1) {
    vans.push_back(pos[i++]);
  }
  while (1) {
    // cerr << vans;
    if (vans.size() + 2 > K)
      break;
    if (i + 1 >= pos.size()) {
      rep(_, 2) vans.push_back(neg[j++]);
      continue;
    }
    if (j + 1 >= neg.size()) {
      rep(_, 2) vans.push_back(pos[i++]);
      continue;
    }
    int p = pos[i] * pos[i + 1];
    int n = neg[j] * neg[j + 1];
    if (p > n) {
      vans.push_back(pos[i]);
      vans.push_back(pos[i + 1]);
      i += 2;
    } else {
      vans.push_back(neg[j]);
      vans.push_back(neg[j + 1]);
      j += 2;
    }
  }

  rep(i, K)(ans *= vans[i]) %= MOD;
  cout << ans << endl;
  return 0;
}

Error: 0

Fixed submission:

#include <algorithm>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

#define MOD 1000000007
#define MOD2 998244353
#define int long long
#define double long double
#define EPS 1e-9
// #define PI 3.14159265358979

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

using namespace std;

template <typename T> ostream &operator<<(ostream &os, const vector<T> &A) {
  for (int i = 0; i < A.size(); i++)
    os << A[i] << " ";
  os << endl;
  return os;
}
template <> ostream &operator<<(ostream &os, const vector<vector<int>> &A) {
  int N = A.size();
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < A[i].size(); j++)
      os << A[i][j] << " ";
    os << endl;
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}

typedef pair<int, int> pii;
typedef long long ll;

struct edge {
  int from, to, d, c, i;
  edge(int _from = 0, int _to = 0, int _d = 0, int _c = 0) {
    from = _from;
    to = _to;
    d = _d;
    c = _c;
  }
  bool operator<(const edge &rhs) const {
    return (d == rhs.d) ? (c < rhs.c) : (d < rhs.d);
  }
};
struct aabb {
  int x1, y1, x2, y2;
  aabb(int x1, int y1, int x2, int y2) : x1(x1), y1(y1), x2(x2), y2(y2) {}
};

typedef vector<edge> edges;
typedef vector<edges> graph;
struct flow {
  int to, cap, rev, cost;
  flow(int to = 0, int cap = 0, int rev = 0, int cost = 0)
      : to(to), cap(cap), rev(rev), cost(cost) {}
};
typedef vector<vector<flow>> flows;

const int di[4] = {0, -1, 0, 1};
const int dj[4] = {-1, 0, 1, 0};
const int ci[5] = {0, 0, -1, 0, 1};
const int cj[5] = {0, -1, 0, 1, 0};
const ll LINF = LLONG_MAX / 2;
const int INF = INT_MAX / 2;
const double PI = acos(-1);

int pow2(int n) { return 1LL << n; }
template <typename T, typename U> bool chmin(T &x, const U &y) {
  if (x > y) {
    x = y;
    return true;
  }
  return false;
}
template <typename T, typename U> bool chmax(T &x, const U &y) {
  if (x < y) {
    x = y;
    return true;
  }
  return false;
}

template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  fill((T *)array, (T *)(array + N), val);
}
struct initializer {
  initializer() { cout << fixed << setprecision(20); }
};
initializer _____;

int N, M, K, T, Q, H, W;
signed main() {
  cin >> N >> K;
  vector<int> A(N);
  rep(i, N) cin >> A[i];
  if (N == K) {
    int ans = 1;
    rep(i, N)(ans *= A[i]) %= MOD;
    cout << (ans + MOD) % MOD << endl;
    return 0;
  }
  vector<int> Pos, Neg;
  rep(i, N) {
    if (A[i] < 0) {
      Neg.push_back(-A[i]);
    } else {
      Pos.push_back(A[i]);
    }
  }
  if (Pos.size() == 0 && (K & 1)) {
    sort(Neg.begin(), Neg.end());
    int ans = 1;
    rep(i, K) { (ans *= Neg[i]) %= MOD; }
    ans = -ans;
    ans %= MOD;
    ans = (ans + MOD) % MOD;
    cout << ans << endl;
    return 0;
  }
  sort(Pos.rbegin(), Pos.rend());
  sort(Neg.rbegin(), Neg.rend());
  priority_queue<int, vector<int>, greater<int>> q;
  M = Neg.size();
  for (int i = 0; i < M; i += 2) {
    if (i + 1 >= M) {
      if (q.size() != K) {
        q.push(Pos[i]);
      }
      break;
    }
    if (q.size() + 2 > K)
      break;
    q.push(Neg[i]);
    q.push(Neg[i + 1]);
  }
  M = Pos.size();
  for (int i = 0; i + 1 < M; i += 2) {
    if (q.size() + 2 <= K) {
      q.push(Pos[i]);
      q.push(Pos[i + 1]);
    } else {
      int a = q.top();
      q.pop();
      int b = q.top();
      q.pop();
      if (a * b < Pos[i] * Pos[i + 1]) {
        q.push(Pos[i]);
        q.push(Pos[i + 1]);
      } else {
        q.push(a);
        q.push(b);
        if (q.size() != K) {
          q.push(Pos[i]);
        }
        break;
      }
    }
  }
  int ans = 1;
  while (!q.empty()) {
    (ans *= q.top()) %= MOD;
    q.pop();
  }
  cout << ans << endl;
  return 0;
}