Problem p01976 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define stoi stoll
using ll = long long;
using vi = vector<int>;
using pii = pair<int, int>;
#define ALL(c) begin(c), end(c)
#define RALL(c) rbegin(c), rend(c)
#define ITR(i, b, e) for (auto i = (b); i != (e); ++i)
#define FORE(x, c) for (auto &x : c)
#define REPF(i, a, n) for (int i = a, i##len = (int)(n); i < i##len; ++i)
#define REP(i, n) REPF(i, 0, n)
#define REPR(i, n) for (int i = (int)(n); i >= 0; --i)
#define SZ(c) ((int)c.size())
#define CONTAIN(c, x) (c.find(x) != end(c))
#define OUTOFRANGE(y, x, h, w) ((y) < 0 || (x) < 0 || (y) >= (h) || (x) >= (w))
#define dump(...)
const signed INF_ = 1001001001;
const long long INF = 1001001001001001001LL;
const int DX[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0},
          DY[9] = {-1, 0, 1, 0, -1, 1, 1, -1, 0};
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  ITR(i, begin(v), end(v)) os << *i << (i == end(v) - 1 ? "" : " ");
  return os;
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
  ITR(i, begin(v), end(v)) is >> *i;
  return is;
}
template <class T, class U> istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first >> p.second;
  return is;
}
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> using heap = priority_queue<T, vector<T>, greater<T>>;
struct {
  template <class T> operator T() {
    T x;
    cin >> x;
    return x;
  }
} IN;
struct before_main_function {
  before_main_function() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(15) << fixed;
#define endl "\\n"
  }
} before_main_function;
//------------------8<------------------------------------8<--------------------

signed main() {
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  map<int, int> f, b;
  vector<int> ans;
  REP(i, n) {
    f[a[i]]++;
    b[a[n - 1 - i]]++;
    if (f == b) {
      ans.push_back(i + 1);
    }
  }
  cout << ans << endl;
  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define stoi stoll
using ll = long long;
using vi = vector<int>;
using pii = pair<int, int>;
#define ALL(c) begin(c), end(c)
#define RALL(c) rbegin(c), rend(c)
#define ITR(i, b, e) for (auto i = (b); i != (e); ++i)
#define FORE(x, c) for (auto &x : c)
#define REPF(i, a, n) for (int i = a, i##len = (int)(n); i < i##len; ++i)
#define REP(i, n) REPF(i, 0, n)
#define REPR(i, n) for (int i = (int)(n); i >= 0; --i)
#define SZ(c) ((int)c.size())
#define CONTAIN(c, x) (c.find(x) != end(c))
#define OUTOFRANGE(y, x, h, w) ((y) < 0 || (x) < 0 || (y) >= (h) || (x) >= (w))
#define dump(...)
const signed INF_ = 1001001001;
const long long INF = 1001001001001001001LL;
const int DX[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0},
          DY[9] = {-1, 0, 1, 0, -1, 1, 1, -1, 0};
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  ITR(i, begin(v), end(v)) os << *i << (i == end(v) - 1 ? "" : " ");
  return os;
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
  ITR(i, begin(v), end(v)) is >> *i;
  return is;
}
template <class T, class U> istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first >> p.second;
  return is;
}
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> using heap = priority_queue<T, vector<T>, greater<T>>;
struct {
  template <class T> operator T() {
    T x;
    cin >> x;
    return x;
  }
} IN;
struct before_main_function {
  before_main_function() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(15) << fixed;
#define endl "\\n"
  }
} before_main_function;
//------------------8<------------------------------------8<--------------------

signed main() {
  int n;
  cin >> n;
  vector<int> a(n);
  cin >> a;
  multiset<int> f, b;
  vector<int> ans;
  REP(i, n) {
    f.insert(a[i]);
    b.insert(a[n - 1 - i]);
    if (f == b) {
      ans.push_back(i + 1);
    }
  }
  cout << ans << endl;
  return 0;
}