Language: C++

#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#define REP(i, b, n) for (Int i = b; i < Int(n); i++)
#define rep(i, n) REP(i, 0, n)
using namespace std;
using Int = long long;
Int inf = 1000000000000000001LL;
using vi = vector<Int>;
using vvi = vector<vi>;

Int GCD(Int a, Int b){
    if(b==0) return a;
    if(a < b) return GCD(b, a);
    unsigned r;
    while ((r=a%b)) {
        a = b;
        b = r;
    }
    return b;
}
int binary_search_index(Int Y, vi &q){
    int left = 0, right = q.size() - 1;
    while (right >= left) {
        int mid = left + (right - left) / 2;
        if (q[mid] == Y) return mid;
        else if (q[mid] > Y) right = mid - 1;
        else if (q[mid] < Y) left = mid + 1;
    }
    return -1;
}

int main() {
    Int N;
    cin >>N;
    vi v = vi(N);
    rep(i,N){
        cin >> v[i];
    }
    map<int,int> v_odd;
    map<int,int> v_even;

    pair<int,int> v_odd_max = pair<int,int>(-1,0);
    pair<int,int> v_even_max = pair<int,int>(-1,0);
    pair<int,int> v_odd_max2 = pair<int,int>(-1,0);
    pair<int,int> v_even_max2 = pair<int,int>(-1,0);

    for(int i =0; i<N; i+=2){
        v_even[v[i]]++;
        if(v_even_max.second < v_even[v[i]]){
            v_even_max.first = v[i];
            v_even_max.second = v_even[v[i]];
        }else if (v_even_max.second == v_even[v[i]]){
            v_even_max2.first = v[i];
            v_even_max2.second = v_even[v[i]];
        }
    }

    for(int i =1; i<N; i+=2){
        v_odd[v[i]]++;
        if(v_odd_max.second < v_odd[v[i]]){
            v_odd_max.first = v[i];
            v_odd_max.second = v_odd[v[i]];
        }else if (v_odd_max.second == v_odd[v[i]]){
            v_odd_max2.first = v[i];
            v_odd_max2.second = v_odd[v[i]];
        }
    }

    int odd_ans =0;
    int even_ans =0;

    for (const auto& v : v_even){
        if(v.first != v_even_max.first){
            even_ans += v.second;
        }
    }

    for (const auto& v : v_odd){
        if(v.first != v_odd_max.first){
            odd_ans += v.second;
        }
    }

    if(v_odd_max.first == v_even_max.first){
        if(v_odd_max2.first != -1){
            //odd_ans += min(v_odd_max2.second, v_even_max.second);
        }else if(v_even_max2.first != -1){
            //odd_ans += min(v_even_max2.second, v_odd_max.second);
        }
        else{
            odd_ans += min(v_odd_max.second,v_even_max.second);
        }
    }

    int ans = odd_ans + even_ans;
    cout << ans << endl;

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:38:5: error: 'cin' was not declared in this scope
   38 |     cin >>N;
      |     ^~~
a.cc:7:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    6 | #include <vector>
  +++ |+#include <iostream>
    7 | #define REP(i, b, n) for (Int i = b; i < Int(n); i++)
a.cc:43:5: error: 'map' was not declared in this scope
   43 |     map<int,int> v_odd;
      |     ^~~
a.cc:7:1: note: 'std::map' is defined in header '<map>'; this is probably fixable by adding '#include <map>'
    6 | #include <vector>
  +++ |+#include <map>
    7 | #define REP(i, b, n) for (Int i = b; i < Int(n); i++)
a.cc:43:9: error: expected primary-expression before 'int'
   43 |     map<int,int> v_odd;
      |         ^~~
a.cc:44:9: error: expected primary-expression before 'int'
   44 |     map<int,int> v_even;
      |         ^~~
a.cc:52:9: error: 'v_even' was not declared in this scope; did you mean 'v_even_max'?
   52 |         v_even[v[i]]++;
      |         ^~~~~~
      |         v_even_max
a.cc:63:9: error: 'v_odd' was not declared in this scope
   63 |         v_odd[v[i]]++;
      |         ^~~~~
a.cc:76:26: error: 'v_even' was not declared in this scope; did you mean 'v_even_max'?
   76 |     for (const auto& v : v_even){
      |                          ^~~~~~
      |                          v_even_max
a.cc:82:26: error: 'v_odd' was not declared in this scope
   82 |     for (const auto& v : v_odd){
      |                          ^~~~~
a.cc:100:5: error: 'cout' was not declared in this scope
  100 |     cout << ans << endl;
      |     ^~~~
a.cc:100:5: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'