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: Accepted)

#include <bits/stdc++.h>

using namespace std;
vector<int>f1(100001);
vector<int>f2(100001);

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin>>n;
    for(int i=0; i<n; i++)
    {
        int d;
        cin>>d;
        if(i%2==0)
            f1[d]++;
        else
            f2[d]++;
    }
    vector<int>::iterator  max1=max_element(f1.begin(),f1.end());
    vector<int>::iterator  max2=max_element(f2.begin(),f2.end());
   // cout<<*max1<<' '<<*max2<<endl;
    if((max1-f1.begin())==(max2-f2.begin()) )
    {
        if(*max1!=n/2 && *max2!=n/2)
        {
            if(*max1>*max2)
            {
                *max2=-1;
                max2=max_element(f2.begin(),f2.end());
            }
            else if(*max1==*max2)
            {
                *max1*=-1;
                *max2*=-1;
               vector<int>::iterator smax1=max_element(f1.begin(),f1.end());
               vector<int>::iterator smax2=max_element(f2.begin(),f2.end());
                if(*smax1>=*smax2)
                {
                    *max1=*smax1;
                    *max2*=-1;
                }
                else
                {
                    *max2=*smax2;
                    *max1*=-1;
                }
            }
            else
            {
                *max1=-1;
                max1=max_element(f1.begin(),f1.end());
            }

        }
        else
        {
            if(*max1==n/2 && *max2==n/2)
            {
                *max2=-1;
                max2=max_element(f2.begin(),f2.end());
            }
            else if(*max1==n/2)
            {
                *max2=-1;
                max2=max_element(f2.begin(),f2.end());
            }
            else
            {
                *max1=-1;
                max1=max_element(f1.begin(),f1.end());
            }
        }
    }
    cout<<(n/2-*max1)+(n/2-*max2)<<endl;
    return 0;
}