Problem p03171 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <chrono>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace std::chrono;
using namespace __gnu_pbds;
#define fastio                                                                 \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0)
#define fi first
#define se second
#define int long long
#define pb push_back
#define emp emplace_back
#define vv(x) vector<x>
#define mp(x, y) map<x, y>
#define dq(x) deque<x>
#define pql(x) priority_queue<x>
#define pqs(x) priority_queue<x, vv(x), greater<x>>
#define M 1000000007
#define forf(i, a, b) for (int i = a; i < b; i++)
#define it(x) x::iterator
#define ll long long
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#define time__(d)                                                              \
  for (long blockTime = 0;                                                     \
       (blockTime == 0 ? (blockTime = clock()) != 0 : false);                  \
       debug("%s time : %.4fs", d,                                             \
             (double)(clock() - blockTime) / CLOCKS_PER_SEC))
#define vii vector<int>
#define big 3e18
#define sm -2e9
#define mkr make_pair
#define vpi vector<pair<int, int>>
#define pii pair<int, int>
#define rng 500005
#define sz(x) (int)x.size()
#define rv(x) reverse(x.begin(), x.end())
#define out(x) cout << x.fi << " " << x.se << endl;

// #define ordered_set tree<pii, null_type,less<pii>,
// rb_tree_tag,tree_order_statistics_node_update>

void pr_init() {

#ifndef ONLINE_JUDGE
  freopen("gin.txt", "r", stdin);
  freopen("gout.txt", "w", stdout);

#endif
}

int a[301], dp[3001][3001][2], n;

int recur(int i, int j, int x) {
  if (i == j) {
    return (x % 2 ? -1 : 1) * a[i];
  }
  if (dp[i][j][x] != -1)
    return dp[i][j][x];

  if (!x) {
    dp[i][j][x] = max(a[i] + recur(i + 1, j, (x + 1) % 2),
                      a[j] + recur(i, j - 1, (x + 1) % 2));
  } else {
    dp[i][j][x] = min(recur(i + 1, j, (x + 1) % 2) - a[i],
                      recur(i, j - 1, (x + 1) % 2) - a[j]);
  }

  return dp[i][j][x];
}

void solve() {

  cin >> n;

  forf(i, 0, 3001) { forf(j, 0, 3001) dp[i][j][0] = dp[i][j][1] = -1; }

  forf(i, 1, n + 1) cin >> a[i];

  cout << recur(1, n, 0);
}

int32_t main() {
  pr_init();
  // fastio;

  auto start = high_resolution_clock::now();

  solve();
  auto stop = high_resolution_clock::now();
  auto duration = duration_cast<microseconds>(stop - start);
  // cout << "Time taken by function: "
  //       << duration.count() << " microseconds" << endl;
}


Fixed submission:
#include <bits/stdc++.h>
#include <chrono>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace std::chrono;
using namespace __gnu_pbds;
#define fastio                                                                 \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0)
#define fi first
#define se second
#define int long long
#define pb push_back
#define emp emplace_back
#define vv(x) vector<x>
#define mp(x, y) map<x, y>
#define dq(x) deque<x>
#define pql(x) priority_queue<x>
#define pqs(x) priority_queue<x, vv(x), greater<x>>
#define M 1000000007
#define forf(i, a, b) for (int i = a; i < b; i++)
#define it(x) x::iterator
#define ll long long
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#define time__(d)                                                              \
  for (long blockTime = 0;                                                     \
       (blockTime == 0 ? (blockTime = clock()) != 0 : false);                  \
       debug("%s time : %.4fs", d,                                             \
             (double)(clock() - blockTime) / CLOCKS_PER_SEC))
#define vii vector<int>
#define big 3e18
#define sm -2e9
#define mkr make_pair
#define vpi vector<pair<int, int>>
#define pii pair<int, int>
#define rng 500005
#define sz(x) (int)x.size()
#define rv(x) reverse(x.begin(), x.end())
#define out(x) cout << x.fi << " " << x.se << endl;

// #define ordered_set tree<pii, null_type,less<pii>,
// rb_tree_tag,tree_order_statistics_node_update>

void pr_init() {

#ifndef ONLINE_JUDGE
  freopen("gin.txt", "r", stdin);
  freopen("gout.txt", "w", stdout);

#endif
}

int a[3001], dp[3001][3001][2], n;

int recur(int i, int j, int x) {
  if (i == j) {
    return (x % 2 ? -1 : 1) * a[i];
  }
  if (dp[i][j][x] != -1)
    return dp[i][j][x];

  if (!x) {
    dp[i][j][x] = max(a[i] + recur(i + 1, j, (x + 1) % 2),
                      a[j] + recur(i, j - 1, (x + 1) % 2));
  } else {
    dp[i][j][x] = min(recur(i + 1, j, (x + 1) % 2) - a[i],
                      recur(i, j - 1, (x + 1) % 2) - a[j]);
  }

  return dp[i][j][x];
}

void solve() {

  cin >> n;

  forf(i, 0, 3001) { forf(j, 0, 3001) dp[i][j][0] = dp[i][j][1] = -1; }

  forf(i, 1, n + 1) cin >> a[i];

  cout << recur(1, n, 0);
}

int32_t main() {
  pr_init();
  // fastio;

  auto start = high_resolution_clock::now();

  solve();
  auto stop = high_resolution_clock::now();
  auto duration = duration_cast<microseconds>(stop - start);
  // cout << "Time taken by function: "
  //       << duration.count() << " microseconds" << endl;
}