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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>
#include <vector>

using namespace std;

const int num_elem = 100000;

int main()
{
    int N, v;
    cin >> N;
    vector<int> array1(num_elem), array2(num_elem);
    for (int i = 0; i < N; i++)
    {
        cin >> v;
        if (i % 2 == 0)
        {
            ++array1[--v];
        }
        else
        {
            ++array2[--v];
        }
    }

    int max1 = 0, max1_i, max2 = 0, max2_i;
    for (int i = 0; i < num_elem; i++)
    {
        if (max1 < array1[i])
        {
            max1 = array1[i];
            max1_i = i;
        }
        // even
        if (max2 < array2[i])
        {
            max2 = array2[i];
            max2_i = i;
        }
    }

    if (max1_i == max2_i)
    {
        if (max1 > max2)
        {
            max2 = 0;
            array2[max2_i] = 0;
            for (int i = 1; i < num_elem; i += 2)
            {
                if (max2 < array2[i])
                {
                    max2 = array2[i];
                }
            }
        }
        else
        {
            max1 = 0;
            array1[max1_i] = 0;
            for (int i = 0; i < num_elem; i += 2)
            {
                if (max1 < array1[i])
                {
                    max1 = array1[i];
                }
            }
        }
    }
    cout << N - max2 - max1 << endl;
}