Problem p02779 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> l_l;
typedef pair<int, int> i_i;
typedef vector<ll> vl;
typedef vector<int> vi;
typedef vector<char> vec;
typedef vector<bool> veb;
typedef vector<string> ves;
typedef vector<vector<ll>> vvl;
typedef vector<vector<int>> vvi;
typedef vector<vector<char>> vvec;
typedef vector<vector<bool>> vveb;
typedef vector<vector<string>> vves;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n); i++)
#define rep2(i, n) for (int i = 2; i < (int)(n); i++)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define fs first
#define sc second
#define pb push_back
#define pp pop_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define maxel(a) *max_element(all(a))
#define minel(a) *min_element(all(a))
#define acc accumulate
#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define mod (1000000007)
typedef long long int64;
// const int64 INF = 1LL << 58;
#define dame                                                                   \
  {                                                                            \
    puts("-1");                                                                \
    return 0;                                                                  \
  }
#define YES                                                                    \
  {                                                                            \
    cout << "YES" << endl;                                                     \
    return 0;                                                                  \
  }
#define NO                                                                     \
  {                                                                            \
    cout << "NO" << endl;                                                      \
    return 0;                                                                  \
  }
#define Yes                                                                    \
  {                                                                            \
    cout << "Yes" << endl;                                                     \
    return 0;                                                                  \
  }
#define No                                                                     \
  {                                                                            \
    cout << "No" << endl;                                                      \
    return 0;                                                                  \
  }
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;
}
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  ll n;
  cin >> n;
  vl a(n);
  rep(i, n) cin >> a[i];
  rep(i, n) {
    repk(j, i, n) {
      if (a[i] == a[j] && i != j) {
        NO;
        return 0;
      }
    }
  }
  YES;
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> l_l;
typedef pair<int, int> i_i;
typedef vector<ll> vl;
typedef vector<int> vi;
typedef vector<char> vec;
typedef vector<bool> veb;
typedef vector<string> ves;
typedef vector<vector<ll>> vvl;
typedef vector<vector<int>> vvi;
typedef vector<vector<char>> vvec;
typedef vector<vector<bool>> vveb;
typedef vector<vector<string>> vves;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n); i++)
#define rep2(i, n) for (int i = 2; i < (int)(n); i++)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define fs first
#define sc second
#define pb push_back
#define pp pop_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define maxel(a) *max_element(all(a))
#define minel(a) *min_element(all(a))
#define acc accumulate
#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define mod (1000000007)
typedef long long int64;
// const int64 INF = 1LL << 58;
#define dame                                                                   \
  {                                                                            \
    puts("-1");                                                                \
    return 0;                                                                  \
  }
#define YES                                                                    \
  {                                                                            \
    cout << "YES" << endl;                                                     \
    return 0;                                                                  \
  }
#define NO                                                                     \
  {                                                                            \
    cout << "NO" << endl;                                                      \
    return 0;                                                                  \
  }
#define Yes                                                                    \
  {                                                                            \
    cout << "Yes" << endl;                                                     \
    return 0;                                                                  \
  }
#define No                                                                     \
  {                                                                            \
    cout << "No" << endl;                                                      \
    return 0;                                                                  \
  }
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;
}
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  ll n;
  cin >> n;
  vl a(n);
  rep(i, n) cin >> a[i];
  sort(all(a));
  rep(i, n - 1) {
    if (a[i] == a[i + 1]) {
      NO;
      return 0;
    }
  }
  YES;
  return 0;
}