Problem p03246 (C++)

Buggy submission (status: Runtime Error):
/*
Author : N_o_o_B
Created : June 15 2020 15:42:13
*/
#include <bits/stdc++.h>
using namespace std;
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
*/
#define TRACE
#ifdef TRACE
#define trace(...)                                                             \
  {                                                                            \
    cerr << "[ ";                                                              \
    __trace__(#__VA_ARGS__, __VA_ARGS__);                                      \
  }
#undef endl
template <typename Arg1, typename Arg2>
ostream &operator<<(ostream &out, const pair<Arg1, Arg2> &x) {
  return out << "(" << x.first << "," << x.second << ")";
}

template <typename Arg1>
ostream &operator<<(ostream &out, const vector<Arg1> &a) {
  out << "[";
  for (const auto &x : a)
    out << x << ",";
  return out << "]";
}

template <typename Arg1> ostream &operator<<(ostream &out, const set<Arg1> &a) {
  out << "[";
  for (const auto &x : a)
    out << x << ",";
  return out << "]";
}

template <typename Arg1, typename Arg2>
ostream &operator<<(ostream &out, const map<Arg1, Arg2> &a) {
  out << "[";
  for (const auto &x : a)
    out << x << ",";
  return out << "]";
}

template <typename Arg1> void __trace__(const string name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << " ] " << endl;
}

template <typename Arg1, typename... Args>
void __trace__(const string names, Arg1 &&arg1, Args &&...args) {
  const string name = names.substr(0, names.find(','));
  cerr << name << " : " << arg1 << " | ";
  __trace__(names.substr(1 + (int)name.size()), args...);
}
#else
#define trace(args...)
#endif

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int>> vii;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vl> vvl;
// typedef tree<pii, null_type, less<pii>, rb_tree_tag,
// tree_order_statistics_node_update> oset;
#define fori(i, n) for (int i = 0; i < n; i++)
#define rep(i, a, b) for (int i = a; i <= b; i++)
#define repd(i, a, b) for (int i = a; i >= b; i--)
#define ford(i, n) for (int i = n - 1; i >= 0; i--)
#define trav(x, a) for (auto &x : a)
#define all(x) x.begin(), x.end()
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define fi first
#define se second
clock_t time_p = clock();
void time_taken() {
  time_p = clock() - time_p;
  cerr << "Time Taken : " << (float)(time_p) / CLOCKS_PER_SEC << "\n";
}
// const ll mod=998244353;
const ll mod = 1e9 + 7;
const ll INF = 1e18;

const int maxn = 1e5 + 5;

int cnt[2][maxn];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cout.precision(12);
  cout << fixed;
  int n;
  cin >> n;
  set<int> s;
  fori(i, n) {
    int x;
    cin >> x;
    cnt[i % 2][x]++;
    if (i % 2) {
      s.insert(x);
    }
  }
  map<int, int> m;
  for (auto x : s) {
    m[cnt[1][x]]++;
  }
  int ans = n;
  for (int i = 1; i <= maxn; i++) {
    int cur = n / 2 - cnt[0][i];
    if (m.rbegin()->first == cnt[1][i]) {
      if (m.rbegin()->second == 1) {
        m.erase(m.rbegin()->fi);
        cur += n / 2 - (sz(m) ? m.rbegin()->fi : 0);
        m[cnt[1][i]] = 1;
      } else {
        cur += n / 2 - m.rbegin()->fi;
      }
    } else {
      cur += n / 2 - m.rbegin()->fi;
    }
    ans = min(ans, cur);
  }
  cout << ans << endl;

  time_taken();
  return 0;
}

Fixed submission:
/*
Author : N_o_o_B
Created : June 15 2020 15:42:13
*/
#include <bits/stdc++.h>
using namespace std;
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
*/
#define TRACE
#ifdef TRACE
#define trace(...)                                                             \
  {                                                                            \
    cerr << "[ ";                                                              \
    __trace__(#__VA_ARGS__, __VA_ARGS__);                                      \
  }
#undef endl
template <typename Arg1, typename Arg2>
ostream &operator<<(ostream &out, const pair<Arg1, Arg2> &x) {
  return out << "(" << x.first << "," << x.second << ")";
}

template <typename Arg1>
ostream &operator<<(ostream &out, const vector<Arg1> &a) {
  out << "[";
  for (const auto &x : a)
    out << x << ",";
  return out << "]";
}

template <typename Arg1> ostream &operator<<(ostream &out, const set<Arg1> &a) {
  out << "[";
  for (const auto &x : a)
    out << x << ",";
  return out << "]";
}

template <typename Arg1, typename Arg2>
ostream &operator<<(ostream &out, const map<Arg1, Arg2> &a) {
  out << "[";
  for (const auto &x : a)
    out << x << ",";
  return out << "]";
}

template <typename Arg1> void __trace__(const string name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << " ] " << endl;
}

template <typename Arg1, typename... Args>
void __trace__(const string names, Arg1 &&arg1, Args &&...args) {
  const string name = names.substr(0, names.find(','));
  cerr << name << " : " << arg1 << " | ";
  __trace__(names.substr(1 + (int)name.size()), args...);
}
#else
#define trace(args...)
#endif

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int>> vii;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vl> vvl;
// typedef tree<pii, null_type, less<pii>, rb_tree_tag,
// tree_order_statistics_node_update> oset;
#define fori(i, n) for (int i = 0; i < n; i++)
#define rep(i, a, b) for (int i = a; i <= b; i++)
#define repd(i, a, b) for (int i = a; i >= b; i--)
#define ford(i, n) for (int i = n - 1; i >= 0; i--)
#define trav(x, a) for (auto &x : a)
#define all(x) x.begin(), x.end()
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define fi first
#define se second
clock_t time_p = clock();
void time_taken() {
  time_p = clock() - time_p;
  cerr << "Time Taken : " << (float)(time_p) / CLOCKS_PER_SEC << "\n";
}
// const ll mod=998244353;
const ll mod = 1e9 + 7;
const ll INF = 1e18;

const int maxn = 1e5 + 5;

int cnt[2][maxn];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cout.precision(12);
  cout << fixed;
  int n;
  cin >> n;
  set<int> s;
  fori(i, n) {
    int x;
    cin >> x;
    cnt[i % 2][x]++;
    if (i % 2) {
      s.insert(x);
    }
  }
  map<int, int> m;
  for (auto x : s) {
    m[cnt[1][x]]++;
  }
  int ans = n;
  for (int i = 1; i < maxn; i++) {
    int cur = n / 2 - cnt[0][i];
    if (m.rbegin()->first == cnt[1][i]) {
      if (m.rbegin()->second == 1) {
        m.erase(m.rbegin()->fi);
        cur += n / 2 - (sz(m) ? m.rbegin()->fi : 0);
        m[cnt[1][i]] = 1;
      } else {
        cur += n / 2 - m.rbegin()->fi;
      }
    } else {
      cur += n / 2 - m.rbegin()->fi;
    }
    ans = min(ans, cur);
  }
  cout << ans << endl;

  time_taken();
  return 0;
}