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

#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
// #pragma GCC optimize(3)
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// #pragma GCC target("sse3","sse2","sse")
// #pragma GCC target("avx","sse4","sse4.1","sse4.2","ssse3")
// #pragma GCC target("f16c")
// #pragma GCC
// optimize("inline","fast-math","unroll-loops","no-stack-protector") #pragma
// GCC diagnostic error "-fwhole-program" #pragma GCC diagnostic error
// "-fcse-skip-blocks" #pragma GCC diagnostic error
// "-funsafe-loop-optimizations" #pragma GCC diagnostic error "-std=c++14"
#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"

#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define REP(x, l, u) for (ll x = l; x < u; x++)
#define RREP(x, l, u) for (ll x = l; x >= u; x--)
#define complete_unique(a) a.erase(unique(begin(a), end(a)), end(a))
#define mst(x, a) memset(x, a, sizeof(x))
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define MP make_pair
#define lowbit(x) ((x) & (-(x)))
#define bitcnt(x) (__builtin_popcountll(x))
#define lson (ind << 1)
#define rson (ind << 1 | 1)
#define se second
#define fi first
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace __gnu_pbds; // required
using namespace std;
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef vector<ll> VLL;
typedef vector<int> VI;
const ll mod = 1e9 + 7;

string to_string(string s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define dbg(...)                                                               \\
  {}
#endif

template <typename T, typename S> inline bool upmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}

template <typename T, typename S> inline bool upmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}

ull twop(ll x) { return 1ULL << x; }

ll MOD(ll a, ll m) {
  a %= m;
  if (a < 0)
    a += m;
  return a;
}

ll inverse(ll a, ll m) {
  a = MOD(a, m);
  if (a <= 1)
    return a;
  return MOD((1 - inverse(m, a) * m) / a, m);
}

template <typename T> T sqr(T x) { return x * x; }

ll gcd(ll a, ll b) {
  a = abs(a), b = abs(b);
  while (b != 0) {
    a %= b;
    swap(a, b);
  }
  return a;
}

ll fast(ll a, ll b, ll mod) {
  a %= mod;
  if (b < 0)
    a = inverse(a, mod), b = -b;
  ll ans = 1;
  while (b) {
    if (b & 1)
      ans = ans * a % mod;
    a = a * a % mod;
    b /= 2;
  }
  return ans % mod;
}

namespace SOLVE {
void main() {
  ll n, k;
  VLL pos, neg, tot;
  cin >> n >> k;
  REP(i, 0, n) {
    ll c;
    cin >> c;
    if (c >= 0)
      pos.PB(c);
    else
      neg.PB(-c);
    tot.PB(c);
  }
  sort(all(pos));
  sort(all(neg));
  if (min(sz(neg), (int)k) / 2 * 2 + sz(pos) < k) {
    ll ans = 1;
    pos.insert(end(pos), all(neg));
    sort(all(pos));
    dbg(pos);
    REP(i, 0, k) ans = ans * pos[i] % mod;
    cout << MOD(-ans, mod) << endl;
    return;
  }
  ll cnt = 0;
  multiset<int> s;
  REP(i, 0, k) {
    if (sz(pos) and sz(neg)) {
      if (pos.back() > neg.back()) {
        s.insert(pos.back());
        pos.pop_back();
      } else {
        s.insert(-neg.back());
        neg.pop_back();
        cnt++;
      }
    } else if (sz(pos)) {
      s.insert(pos.back());
      pos.pop_back();
    } else {
      s.insert(-neg.back());
      neg.pop_back();
      cnt++;
    }
  }
  if (cnt & 1) {
    dbg(cnt, s);
    bool a = 0, b = 0;
    ll p0, p1, n0, n1;
    if (sz(pos)) {
      a = 1;
      p0 = pos.back();
      n1 = *(--s.lower_bound(0));
    }
    if (sz(neg) and cnt < k) {
      b = 1;
      n0 = -neg.back();
      p1 = *s.lower_bound(0);
    }
    dbg(a, b);
    assert(a or b);
    if (a and b) {
      dbg(p0, p1, n0, n1);
      if (p0 * p1 > n0 * n1) {
        dbg("pos");
        s.erase(s.find(n1));
        s.insert(p0);
      } else {
        s.erase(s.find(p1));
        s.insert(n0);
      }
    } else if (a) {
      s.erase(s.find(n1));
      s.insert(p0);
    } else {
      s.erase(s.find(p1));
      s.insert(n0);
    }
  }
  ll a = 1;
  for (auto i : s)
    a = a * i % mod;
  cout << MOD(a, mod);
}
} // namespace SOLVE

signed main() {
#ifdef LOCAL
  fr("/Users/zhangqingchuan/Desktop/cp/cp/input.txt");
  fw("/Users/zhangqingchuan/Desktop/cp/cp/output.txt");
#endif
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);

  int t = 1;
  //    cin >> t;
  for (int i = 1; i <= t; i++) {
    //        cout<<"Case #"<<i<<": ";
    SOLVE::main();
  }

  //    clock_t st = clock();
  //    while(clock() - st < 3.0 * CLOCKS_PER_SEC){
  //
  //    }

  return 0;
}


Error: WA

Fixed submission:

#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
// #pragma GCC optimize(3)
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// #pragma GCC target("sse3","sse2","sse")
// #pragma GCC target("avx","sse4","sse4.1","sse4.2","ssse3")
// #pragma GCC target("f16c")
// #pragma GCC
// optimize("inline","fast-math","unroll-loops","no-stack-protector") #pragma
// GCC diagnostic error "-fwhole-program" #pragma GCC diagnostic error
// "-fcse-skip-blocks" #pragma GCC diagnostic error
// "-funsafe-loop-optimizations" #pragma GCC diagnostic error "-std=c++14"
#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"

#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define REP(x, l, u) for (ll x = l; x < u; x++)
#define RREP(x, l, u) for (ll x = l; x >= u; x--)
#define complete_unique(a) a.erase(unique(begin(a), end(a)), end(a))
#define mst(x, a) memset(x, a, sizeof(x))
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define MP make_pair
#define lowbit(x) ((x) & (-(x)))
#define bitcnt(x) (__builtin_popcountll(x))
#define lson (ind << 1)
#define rson (ind << 1 | 1)
#define se second
#define fi first
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace __gnu_pbds; // required
using namespace std;
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef vector<ll> VLL;
typedef vector<int> VI;
const ll mod = 1e9 + 7;

string to_string(string s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define dbg(...)                                                               \\
  {}
#endif

template <typename T, typename S> inline bool upmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}

template <typename T, typename S> inline bool upmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}

ull twop(ll x) { return 1ULL << x; }

ll MOD(ll a, ll m) {
  a %= m;
  if (a < 0)
    a += m;
  return a;
}

ll inverse(ll a, ll m) {
  a = MOD(a, m);
  if (a <= 1)
    return a;
  return MOD((1 - inverse(m, a) * m) / a, m);
}

template <typename T> T sqr(T x) { return x * x; }

ll gcd(ll a, ll b) {
  a = abs(a), b = abs(b);
  while (b != 0) {
    a %= b;
    swap(a, b);
  }
  return a;
}

ll fast(ll a, ll b, ll mod) {
  a %= mod;
  if (b < 0)
    a = inverse(a, mod), b = -b;
  ll ans = 1;
  while (b) {
    if (b & 1)
      ans = ans * a % mod;
    a = a * a % mod;
    b /= 2;
  }
  return ans % mod;
}

namespace SOLVE {
void main() {
  ll n, k;
  VLL pos, neg, tot;
  cin >> n >> k;
  REP(i, 0, n) {
    ll c;
    cin >> c;
    if (c >= 0)
      pos.PB(c);
    else
      neg.PB(-c);
    tot.PB(c);
  }
  sort(all(pos));
  sort(all(neg));
  if (min(sz(neg), (int)k) / 2 * 2 + sz(pos) < k) {
    ll ans = 1;

    if (sz(pos) and pos[0] == 0)
      ans = 0;
    pos.insert(end(pos), all(neg));
    sort(all(pos));
    dbg(pos);
    REP(i, 0, k) ans = ans * pos[i] % mod;
    cout << MOD(-ans, mod) << endl;
    return;
  }
  ll cnt = 0;
  VLL ans;
  multiset<int> s;
  REP(i, 0, k) {
    if (sz(pos) and sz(neg)) {
      if (pos.back() > neg.back()) {
        s.insert(pos.back());
        pos.pop_back();
      } else {
        s.insert(-neg.back());
        neg.pop_back();
        cnt++;
      }
    } else if (sz(pos)) {
      s.insert(pos.back());
      pos.pop_back();
    } else {
      s.insert(-neg.back());
      neg.pop_back();
      cnt++;
    }
  }
  dbg(cnt, ans);
  if (cnt & 1) {
    bool a = 0, b = 0;
    ll p0, p1, n0, n1;
    if (sz(pos)) {
      a = 1;
      p0 = pos.back();
      n1 = *(--s.lower_bound(0));
    }
    if (sz(neg) and *s.begin() < 0) {
      b = 1;
      n0 = neg.back();
      p1 = *s.lower_bound(0);
    }
    assert(a or b);
    if (a and b) {
      if (p0 * p1 <= n0 * n1) {
        s.erase(s.find(n1));
        s.insert(p0);
      } else {
        s.erase(s.lower_bound(0));
        s.insert(n0);
      }
    } else if (a) {
      s.erase(s.begin());
      s.insert(p0);
    } else {
      s.erase(s.lower_bound(0));
      s.insert(n0);
    }
  }
  ll a = 1;
  for (auto i : s)
    a = a * i % mod;
  cout << MOD(a, mod);
}
} // namespace SOLVE

signed main() {
#ifdef LOCAL
  fr("/Users/zhangqingchuan/Desktop/cp/cp/input.txt");
  fw("/Users/zhangqingchuan/Desktop/cp/cp/output.txt");
#endif
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);

  int t = 1;
  //    cin >> t;
  for (int i = 1; i <= t; i++) {
    //        cout<<"Case #"<<i<<": ";
    SOLVE::main();
  }

  //    clock_t st = clock();
  //    while(clock() - st < 3.0 * CLOCKS_PER_SEC){
  //
  //    }

  return 0;
}