Problem p03216 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
#define MOD (long long int)(1e9 + 7)
#define ll long long int
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = n - 1; i >= 0; i--)
#define REPS(i, n) for (int i = n; i > 0; i--)
#define FOR(i, a, b) for (int i = a; i < (int)(b); i++)
#define ALL(x) (x).begin(), (x).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define CLR(a) memset((a), 0, sizeof(a))
#define PB push_back
#define MP make_pair
#define SP << " " <<
const int INF = 1001001001;
const ll LINF = 100100100100100100;
const double EPS = 1e-10;
const long double PI = acos(-1.0L);
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef pair<double, double> PDD;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
#define chmax(a, b) a = (((a) < (b)) ? (b) : (a))
#define chmin(a, b) a = (((a) > (b)) ? (b) : (a))

__attribute__((constructor)) void initial() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
}

signed main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int q;
  cin >> q;
  while (q--) {
    int k;
    cin >> k;
    ll ans = 0LL, d = 0LL, m = 0LL, dm = 0LL;
    cerr << "i s[i] ans D M DM" << endl;
    rep(i, n) {
      if (s[i] == 'D')
        d++;
      if (s[i] == 'M')
        m++, dm += d;
      if (s[i] == 'C')
        ans += dm;
      if (i >= k - 1) {
        if (s[i - k + 1] == 'D')
          d--, dm -= m;
        if (s[i - k + 1] == 'M')
          m--;
      }
      cerr << i SP s[i] SP ans SP d SP m SP dm << endl;
    }
    cout << ans << endl;
  }

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define MOD (long long int)(1e9 + 7)
#define ll long long int
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = n - 1; i >= 0; i--)
#define REPS(i, n) for (int i = n; i > 0; i--)
#define FOR(i, a, b) for (int i = a; i < (int)(b); i++)
#define ALL(x) (x).begin(), (x).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define CLR(a) memset((a), 0, sizeof(a))
#define PB push_back
#define MP make_pair
#define SP << " " <<
const int INF = 1001001001;
const ll LINF = 100100100100100100;
const double EPS = 1e-10;
const long double PI = acos(-1.0L);
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef pair<double, double> PDD;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
#define chmax(a, b) a = (((a) < (b)) ? (b) : (a))
#define chmin(a, b) a = (((a) > (b)) ? (b) : (a))

__attribute__((constructor)) void initial() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
}

signed main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int q;
  cin >> q;
  while (q--) {
    int k;
    cin >> k;
    ll ans = 0LL, d = 0LL, m = 0LL, dm = 0LL;
    cerr << "i s[i] ans D M DM" << endl;
    rep(i, n) {
      if (s[i] == 'D')
        d++;
      if (s[i] == 'M')
        m++, dm += d;
      if (s[i] == 'C')
        ans += dm;
      if (i >= k - 1) {
        if (s[i - k + 1] == 'D')
          d--, dm -= m;
        if (s[i - k + 1] == 'M')
          m--;
      }
      // cerr<< i SP s[i] SP ans SP d SP m SP dm<<endl;
    }
    cout << ans << endl;
  }

  return 0;
}