Problem p02716 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
const int inf = 1e9 + 7;
const ll INF = 1e18;
// int mod = 998244353;
int mod = 1000000007;
#define abs(x) (x >= 0 ? x : -(x))
#define lb(v, x) (int)(lower_bound(all(v), x) - v.begin())
#define ub(v, x) (int)(upper_bound(all(v), x) - v.begin())
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
ll pow(ll a, int b) { return b ? pow(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
ll modpow(ll a, ll b, ll _mod) {
  return b ? modpow(a * a % _mod, b / 2, _mod) * (b % 2 ? a : 1) % _mod : 1;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  rep(i, sz(vec)) {
    if (i)
      os << " ";
    os << vec[i];
  }
  return os;
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << p.F << " " << p.S;
  return os;
}
template <typename T> inline istream &operator>>(istream &is, vector<T> &v) {
  rep(j, sz(v)) is >> v[j];
  return is;
}
template <class T, class T2> inline void add(T &a, T2 b) {
  a += b;
  if (a >= mod)
    a -= mod;
}

void solve();

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(10);

  int T;
  // cin >> T;
  T = 1;

  while (T--) {
    solve();
  }
}

// https://atcoder.jp/contests/abc162/submissions/11879810
void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  vector<map<int, ll>> dp(n + 2);
  dp[0][0] = 0;
  rep(i, n) {
    // [0, i - 1] の個数, max sums
    for (const auto &[c, val] : dp[i]) {
      // 0 との max をとらないよう
      if (!dp[i + 1].count(c))
        dp[i + 1][c] = -INF;
      chmax(dp[i + 1][c], dp[i][c]);

      if (!dp[i + 2].count(c + 1))
        dp[i + 2][c + 1] = -INF;
      chmax(dp[i + 2][c + 1], dp[i][c] + a[i]);
    }
  }
  ll ans = -INF;
  rep(i, n + 2) if (dp[i].count(n / 2)) chmax(ans, dp[i][n / 2]);
  cout << ans << endl;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
const int inf = 1e9 + 7;
const ll INF = 1e18;
// int mod = 998244353;
int mod = 1000000007;
#define abs(x) (x >= 0 ? x : -(x))
#define lb(v, x) (int)(lower_bound(all(v), x) - v.begin())
#define ub(v, x) (int)(upper_bound(all(v), x) - v.begin())
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
ll pow(ll a, int b) { return b ? pow(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
ll modpow(ll a, ll b, ll _mod) {
  return b ? modpow(a * a % _mod, b / 2, _mod) * (b % 2 ? a : 1) % _mod : 1;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  rep(i, sz(vec)) {
    if (i)
      os << " ";
    os << vec[i];
  }
  return os;
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << p.F << " " << p.S;
  return os;
}
template <typename T> inline istream &operator>>(istream &is, vector<T> &v) {
  rep(j, sz(v)) is >> v[j];
  return is;
}
template <class T, class T2> inline void add(T &a, T2 b) {
  a += b;
  if (a >= mod)
    a -= mod;
}

void solve();

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(10);

  int T;
  // cin >> T;
  T = 1;

  while (T--) {
    solve();
  }
}

// https://atcoder.jp/contests/abc162/submissions/11879810
void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  vector<map<int, ll>> dp(n + 2);
  dp[0][0] = 0;
  rep(i, n) {
    // [0, i - 1] の個数, max sums
    for (const auto &[c, val] : dp[i]) {
      // ないと tle
      if (c < i / 2 - 1 || c > (i + 1) / 2)
        continue;
      // 0 との max をとらないよう
      if (!dp[i + 1].count(c))
        dp[i + 1][c] = -INF;
      chmax(dp[i + 1][c], dp[i][c]);

      if (!dp[i + 2].count(c + 1))
        dp[i + 2][c + 1] = -INF;
      chmax(dp[i + 2][c + 1], dp[i][c] + a[i]);
    }
  }
  ll ans = -INF;
  rep(i, n + 2) if (dp[i].count(n / 2)) chmax(ans, dp[i][n / 2]);
  cout << ans << endl;
}