Problem p02709 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define per(i, n) for (ll i = n - 1; i >= 0; i--)
#define perl(i, r, l) for (ll i = r - 1; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x, vector<x>, greater<x>>
#define all(x) (x).begin(), (x).end()
#define CST(x) cout << fixed << setprecision(x)
#define vtpl(x, y, z) vector<tuple<x, y, z>>
#define rev(x) reverse(x);
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[9] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const ll dx[9] = {0, -1, 0, 1, 1, -1, 1, -1, 0};
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
ll n;
vpl v;
ll memo[2010][2010];
ll dfs(ll l, ll r) {
  if (l > r)
    return 0;
  if (memo[l][r] != -1)
    return memo[l][r];
  ll now = n - (r + 1 - l);
  ll ret1 = v[now].fi * abs(v[now].se - l);
  ll ret2 = v[now].fi * abs(v[now].se - r);
  ll ret = max(ret1 + dfs(l + 1, r), ret2 + dfs(l, r - 1));
  memo[l][r] = ret;
  return ret;
}
int main() {
  cin >> n;
  v.resize(n);
  rep(i, n) {
    ll a;
    cin >> a;
    v[i] = {a, i};
  }
  sort(all(v));
  rev(all(v));
  rep(i, 2010) rep(j, 2010) memo[i][j] = -1;
  cout << dfs(0, n - 1) << endl;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repl(i, l, r) for (ll i = (l); i < (r); i++)
#define per(i, n) for (ll i = n - 1; i >= 0; i--)
#define perl(i, r, l) for (ll i = r - 1; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x, vector<x>, greater<x>>
#define all(x) (x).begin(), (x).end()
#define CST(x) cout << fixed << setprecision(x)
#define vtpl(x, y, z) vector<tuple<x, y, z>>
#define rev(x) reverse(x);
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[9] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const ll dx[9] = {0, -1, 0, 1, 1, -1, 1, -1, 0};
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
ll n;
vpl v;
ll memo[2010][2010];
ll dfs(ll l, ll r) {
  if (l > r)
    return 0;
  ll now = n - (r + 1 - l);
  ll ret1 = v[now].fi * abs(v[now].se - l);
  ll ret2 = v[now].fi * abs(v[now].se - r);
  ll ret = max(ret1 + dfs(l + 1, r), ret2 + dfs(l, r - 1));
  memo[l][r] = ret;
  return ret;
}
int main() {
  cin >> n;
  v.resize(n);
  rep(i, n) {
    ll a;
    cin >> a;
    v[i] = {a, i};
  }
  sort(all(v));
  rev(all(v));
  rep(i, 2010) rep(j, 2010) memo[i][j] = -1;
  cout << dfs(0, n - 1) << endl;
}