Problem:
Score : 300 points

Problem Statement

A sequence a_1,a_2,... ,a_n is said to be /\/\/\/ when the following conditions are satisfied:

For each i = 1,2,..., n-2, a_i = a_{i+2}.

Exactly two different numbers appear in the sequence.

You are given a sequence v_1,v_2,...,v_n whose length is even.
We would like to make this sequence /\/\/\/ by replacing some of its elements.
Find the minimum number of elements that needs to be replaced.

Constraints

2 \leq n \leq 10^5

n is even.

1 \leq v_i \leq 10^5

v_i is an integer.

Input

Input is given from Standard Input in the following format:

n
v_1 v_2 ... v_n

Output

Print the minimum number of elements that needs to be replaced.

Sample Input 1

4
3 1 3 2

Sample Output 1

1

The sequence 3,1,3,2 is not /\/\/\/, but we can make it /\/\/\/ by replacing one of its elements: for example, replace the fourth element to make it 3,1,3,1.

Sample Input 2

6
105 119 105 119 105 119

Sample Output 2

0

The sequence 105,119,105,119,105,119 is /\/\/\/.

Sample Input 3

4
1 1 1 1

Sample Output 3

2

The elements of the sequence 1,1,1,1 are all the same, so it is not /\/\/\/.

Solution in C++ (Clang 10.0.0) (judge verdict: Wrong Answer)

#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <algorithm>
typedef long long ll;
const int maxn = 2e5 + 5;
int cnt[maxn];

int main (int argc, char **argv) {
  int n;
  scanf("%d", &n);
  memset(cnt, 0, sizeof(cnt));
  int v, max1 = 0, max2 = 0;
  int sum = 0;
  for (int i=1; i <= n; i++) {
     scanf("%d", &v);
     if (cnt[v] == 0) {
        sum++;
     }
     cnt[v]++;
     if (i&1) {
       max1 = std::max(max1, cnt[v]);
     } else {
       max2 = std::max(max2, cnt[v]);
     }
  }
  
  int ans;
  if (sum == 1) {
    ans = 2;
  } else {
    ans = n - (max1 + max2);
  }
  printf("%d\n", ans);
  return 0;
}