Problem p02716 (C++) — buggy submission, verdict: Runtime Error

#pragma region template
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vvvld = vector<vvld>;
using vs = vector<string>;
using pll = pair<ll, ll>;
using vp = vector<pll>;
template <typename T> using pqrev = priority_queue<T, vector<T>, greater<T>>;
#define rep(i, n) for (ll i = 0, i##_end = (n); i < i##_end; i++)
#define repb(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repr(i, a, b) for (ll i = (a), i##_end = (b); i < i##_end; i++)
#define reprb(i, a, b) for (ll i = (b)-1, i##_end = (a); i >= i##_end; i--)
#define ALL(a) (a).begin(), (a).end()
#define SZ(x) ((ll)(x).size())
//*
constexpr ll MOD = 1e9 + 7;
/*/
constexpr ll MOD = 998244353;
//*/
constexpr ll INF = 1e+18;
constexpr ld EPS = 1e-12L;
constexpr ld PI = 3.14159265358979323846L;
constexpr ll GCD(ll a, ll b) { return b ? GCD(b, a % b) : a; }
constexpr ll LCM(ll a, ll b) { return a / GCD(a, b) * b; }
template <typename S, typename T> constexpr bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename S, typename T> constexpr bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
#ifdef OJ_LOCAL
#include "dump.hpp"
#else
#define dump(...) ((void)0)
#endif
template <typename T> bool print_(const T &a) {
  cout << a;
  return true;
}
template <typename T> bool print_(const vector<T> &vec) {
  for (auto &a : vec) {
    cout << a;
    if (&a != &vec.back()) {
      cout << " ";
    }
  }
  return false;
}
template <typename T> bool print_(const vector<vector<T>> &vv) {
  for (auto &v : vv) {
    for (auto &a : v) {
      cout << a;
      if (&a != &v.back()) {
        cout << " ";
      }
    }
    if (&v != &vv.back()) {
      cout << "\\n";
    }
  }
  return false;
}
void print() { cout << "\\n"; }
template <typename Head, typename... Tail>
void print(Head &&head, Tail &&...tail) {
  bool f = print_(head);
  if (sizeof...(tail) != 0) {
    cout << (f ? " " : "\\n");
  }
  print(forward<Tail>(tail)...);
}
#pragma endregion

ll n;
vll a;
// unordered_map<ll, ll> dp;
map<ll, ll> dp;

inline ll ph(ll i, ll j) { return i * 1000000 + j; }

ll rec(ll i, ll j) {
  ll mi = i == 0 ? 1 : (i + 1) / 2;
  ll ma = i == n - 1 ? (n - 1) / 2 : i / 2 + 1;
  if (!(mi <= j && j <= ma))
    return -INF;
  if (j == 1)
    return a[i];
  if (dp.count(ph(i, j))) {
    return dp[ph(i, j)];
  }
  ll ret = -INF;
  repr(k, i - 4, i - 1) {
    if (k >= 0) {
      chmax(ret, rec(k, j - 1) + a[i]);
    }
  }
  return dp[ph(i, j)] = ret;
}

void solve() {
  ll ans = -INF;
  chmax(ans, rec(n - 1, n / 2));
  chmax(ans, rec(n - 2, n / 2));
  chmax(ans, rec(n - 3, n / 2));
  // dump(dp);
  print(ans);
}

void solve2() {
  ll ans = -INF;
  ll tmp = 0;
  for (ll i = 0; i < n; i += 2) {
    tmp += a[i];
  }
  dump(tmp);
  chmax(ans, tmp);
  for (ll i = n - 2; i >= 0; i -= 2) {
    tmp -= a[i];
    tmp += a[i + 1];
    dump(tmp);
    chmax(ans, tmp);
  }
  print(ans);
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  cin >> n;
  a.resize(n);
  rep(i, n) { cin >> a[i]; }
  if (n & 1) {
    solve();
  } else {
    solve2();
  }
}


Error: -11

Fixed submission:

#pragma region template
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vvvld = vector<vvld>;
using vs = vector<string>;
using pll = pair<ll, ll>;
using vp = vector<pll>;
template <typename T> using pqrev = priority_queue<T, vector<T>, greater<T>>;
#define rep(i, n) for (ll i = 0, i##_end = (n); i < i##_end; i++)
#define repb(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repr(i, a, b) for (ll i = (a), i##_end = (b); i < i##_end; i++)
#define reprb(i, a, b) for (ll i = (b)-1, i##_end = (a); i >= i##_end; i--)
#define ALL(a) (a).begin(), (a).end()
#define SZ(x) ((ll)(x).size())
//*
constexpr ll MOD = 1e9 + 7;
/*/
constexpr ll MOD = 998244353;
//*/
constexpr ll INF = 1e+18;
constexpr ld EPS = 1e-12L;
constexpr ld PI = 3.14159265358979323846L;
constexpr ll GCD(ll a, ll b) { return b ? GCD(b, a % b) : a; }
constexpr ll LCM(ll a, ll b) { return a / GCD(a, b) * b; }
template <typename S, typename T> constexpr bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename S, typename T> constexpr bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
#ifdef OJ_LOCAL
#include "dump.hpp"
#else
#define dump(...) ((void)0)
#endif
template <typename T> bool print_(const T &a) {
  cout << a;
  return true;
}
template <typename T> bool print_(const vector<T> &vec) {
  for (auto &a : vec) {
    cout << a;
    if (&a != &vec.back()) {
      cout << " ";
    }
  }
  return false;
}
template <typename T> bool print_(const vector<vector<T>> &vv) {
  for (auto &v : vv) {
    for (auto &a : v) {
      cout << a;
      if (&a != &v.back()) {
        cout << " ";
      }
    }
    if (&v != &vv.back()) {
      cout << "\\n";
    }
  }
  return false;
}
void print() { cout << "\\n"; }
template <typename Head, typename... Tail>
void print(Head &&head, Tail &&...tail) {
  bool f = print_(head);
  if (sizeof...(tail) != 0) {
    cout << (f ? " " : "\\n");
  }
  print(forward<Tail>(tail)...);
}
#pragma endregion

ll n;
vll a;

const int N = 5000;
ll dp[N][N];

void solve() {
  rep(i, N) rep(j, N) dp[i][j] = -INF;
  dp[0][0] = 0;
  dp[1][0] = 0;
  dp[1][1] = a[0];
  repr(i, 1, n) {
    repr(j, 1, n / 2 + 1) { chmax(dp[i + 1][j], dp[i - 1][j - 1] + a[i]); }
    rep(j, n / 2 + 1) { chmax(dp[i + 1][j], dp[i][j]); }
  }
  print(dp[n][n / 2]);
}

void solve2() {
  ll ans = 0;
  ll tmp = 0;
  for (ll i = 0; i < n; i += 2) {
    tmp += a[i];
  }
  chmax(ans, tmp);
  for (ll i = n - 2; i >= 0; i -= 2) {
    tmp -= a[i];
    tmp += a[i + 1];
    chmax(ans, tmp);
  }
  print(ans);
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  cin >> n;
  a.resize(n);
  rep(i, n) { cin >> a[i]; }
  if (n & 1) {
    return 11;
    solve();
  } else {
    solve2();
  }
}