Problem p03244 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(j, n) for (int j = 0; j < (n); ++j)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define drep2(j, n) for (int j = (n)-1; j >= 0; --j)
#define srep(i, s, t) for (int i = s; i < t; ++i)
#define srep2(j, s, t) for (int j = s; j < t; ++j)
#define srep3(k, s, t) for (int k = s; j < t; ++k)
#define rng(a) a.begin(), a.end()
#define maxs(x, y) (x = max(x, y))
#define mins(x, y) (x = min(x, y))
#define limit(x, l, r) max(l, min(x, r))
#define lims(x, l, r) (x = max(l, min(x, r)))
#define isin(x, l, r) ((l) <= (x) && (x) < (r))
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcountll
#define uni(x) x.erase(unique(rng(x)), x.end())
#define snuke srand((unsigned)clock() + (unsigned)time(NULL));
#define show(x) cout << #x << " = " << x << endl;
#define PQ(T) priority_queue<T, v(T), greater<T>>
#define bn(x) ((1 << x) - 1)
#define dup(x, y) (((x) + (y)-1) / (y))
#define newline puts("")
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
typedef long long int ll;
typedef unsigned uint;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef set<int> S;
typedef queue<int> Q;
typedef queue<P> QP;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
inline int in() {
  int x;
  scanf("%d", &x);
  return x;
}
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#define dame                                                                   \
  {                                                                            \
    puts("-1");                                                                \
    return 0;                                                                  \
  }
#define yn                                                                     \
  { puts("YES"); }                                                             \
  else {                                                                       \
    puts("NO");                                                                \
  }

int main() {
  int n;
  cin >> n;
  int vl[n / 2];
  int vr[n / 2];
  vi vlPool(10010, 0);
  vi vrPool(10010, 0);
  rep(i, n / 2) {
    cin >> vl[i] >> vr[i];
    vlPool[vl[i]]++;
    vrPool[vr[i]]++;
  }

  int modeL = distance(vlPool.begin(), max_element(rng(vlPool)));
  int modeR = distance(vrPool.begin(), max_element(rng(vrPool)));

  int ans = 0;

  sort(rng(vlPool));
  sort(rng(vrPool));
  reverse(rng(vlPool));
  reverse(rng(vrPool));

  if (modeL != modeR) {
    ans += n / 2 - vlPool[0];
    ans += n / 2 - vrPool[0];
    cout << ans << endl;
  } else {
    if (vlPool[0] > vrPool[0]) {
      ans = n - vlPool[0] - vrPool[1];
      cout << ans << endl;
    } else if (vlPool[0] < vrPool[0]) {
      ans = n - vlPool[1] - vrPool[0];
      cout << ans << endl;
    } else {
      ans = n - vlPool[0] - max(vlPool[1], vrPool[1]);
      cout << ans << endl;
    }
  }
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(j, n) for (int j = 0; j < (n); ++j)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define drep2(j, n) for (int j = (n)-1; j >= 0; --j)
#define srep(i, s, t) for (int i = s; i < t; ++i)
#define srep2(j, s, t) for (int j = s; j < t; ++j)
#define srep3(k, s, t) for (int k = s; j < t; ++k)
#define rng(a) a.begin(), a.end()
#define maxs(x, y) (x = max(x, y))
#define mins(x, y) (x = min(x, y))
#define limit(x, l, r) max(l, min(x, r))
#define lims(x, l, r) (x = max(l, min(x, r)))
#define isin(x, l, r) ((l) <= (x) && (x) < (r))
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcountll
#define uni(x) x.erase(unique(rng(x)), x.end())
#define snuke srand((unsigned)clock() + (unsigned)time(NULL));
#define show(x) cout << #x << " = " << x << endl;
#define PQ(T) priority_queue<T, v(T), greater<T>>
#define bn(x) ((1 << x) - 1)
#define dup(x, y) (((x) + (y)-1) / (y))
#define newline puts("")
#define v(T) vector<T>
#define vv(T) v(v(T))
using namespace std;
typedef long long int ll;
typedef unsigned uint;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef set<int> S;
typedef queue<int> Q;
typedef queue<P> QP;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
inline int in() {
  int x;
  scanf("%d", &x);
  return x;
}
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#define dame                                                                   \
  {                                                                            \
    puts("-1");                                                                \
    return 0;                                                                  \
  }
#define yn                                                                     \
  { puts("YES"); }                                                             \
  else {                                                                       \
    puts("NO");                                                                \
  }

int main() {
  int n;
  cin >> n;
  int vl[n / 2];
  int vr[n / 2];
  vi vlPool(100010, 0);
  vi vrPool(100010, 0);
  rep(i, n / 2) {
    cin >> vl[i] >> vr[i];
    vlPool[vl[i]]++;
    vrPool[vr[i]]++;
  }

  int modeL = distance(vlPool.begin(), max_element(rng(vlPool)));
  int modeR = distance(vrPool.begin(), max_element(rng(vrPool)));

  int ans = 0;

  sort(rng(vlPool));
  sort(rng(vrPool));
  reverse(rng(vlPool));
  reverse(rng(vrPool));

  if (modeL != modeR) {
    ans += n / 2 - vlPool[0];
    ans += n / 2 - vrPool[0];
    cout << ans << endl;
  } else {
    if (vlPool[0] > vrPool[0]) {
      ans = n - vlPool[0] - vrPool[1];
      cout << ans << endl;
    } else if (vlPool[0] < vrPool[0]) {
      ans = n - vlPool[1] - vrPool[0];
      cout << ans << endl;
    } else {
      ans = n - vlPool[0] - max(vlPool[1], vrPool[1]);
      cout << ans << endl;
    }
  }
  return 0;
}