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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
import java.awt.*;
import static java.lang.System.*;
import static java.lang.Math.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(in);
        int n=sc.nextInt();
        int[] v=new int[n];
        HashMap<Integer,Integer> mapE=new HashMap<>();
        HashMap<Integer,Integer> mapO=new HashMap<>();
        HashMap<Integer,Integer> map=new HashMap<>();
        for (int i = 0; i < n; i++) {
            v[i]=sc.nextInt();
            map.put(v[i], map.getOrDefault(v[i], 0)+1);
            if(i%2==0){
                mapE.put(v[i],mapE.getOrDefault(v[i], 0)+1);
            }else{
                mapO.put(v[i], mapO.getOrDefault(v[i],0)+1);
            }
        }
        
        if(map.get(v[0])==n){
            out.println(n/2);
            exit(0);
        }
        
        int Emax=0,Omax=0;
        for(int k:mapE.keySet()){
            Emax=max(Emax,mapE.get(k));
        }
        for(int k:mapO.keySet()){
            Omax=max(Omax,mapO.get(k));
        }
        int tmpE=0,tmpO=0;
        for(int k:mapE.keySet()){
            if(mapE.get(k)==Emax)tmpE=k;
        }
        for(int k:mapO.keySet()){
            if(mapO.get(k)==Omax)tmpO=k;
        }
        int Emax2=0,Omax2=0;
        for(int k:mapE.keySet()){
            if(k!=tmpO)Emax2=max(Emax2,mapE.get(k));
        }
        for(int k:mapO.keySet()){
            if(k!=tmpE)Omax2=max(Omax2,mapO.get(k));
        }
        out.println(min(n-Omax-Emax2,n-Omax2-Emax));
    }
}