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: Wrong Answer)

import java.util.*;

public class Main{

    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int num = scan.nextInt();
        int[] up = new int[100001];
        int[] down = new int[100001];
        for(int i = 0; i < num; i++){
            if(i % 2 == 1){
                up[scan.nextInt()] += 1;
            } else {
                down[scan.nextInt()] += 1;
            }
        }

        // search
        int upFirst = 0;
        int upFirstIndex = 0;
        int upSecond = 0;
        int downFirst = 0;
        int downFirstIndex = 0;
        int downSecond = 0;
        for(int i = 1; i <= 100000; i++){
            if(up[i] > upFirst){
                upFirst = up[i];
                upFirstIndex = i;
            } else if(up[i] > upSecond){
                upSecond = up[i];
            }
            if(down[i] > downFirst){
                downFirst = down[i];
                downFirstIndex = i;
            } else if(down[i] > downSecond){
                downSecond = down[i];
            }
        }

        // answer
        int min = 0;
        if(upFirstIndex != downFirstIndex){
            min = (num / 2 - upFirst) + (num / 2 - downFirst);
        } else {
            min = (num / 2 - upFirst) + (num / 2 - downSecond);
            if((num / 2 - downFirst) + (num / 2 - upSecond) < min){
                min = (num / 2 - downFirst) + (num / 2 - upSecond);
            }
        }    
        System.out.println(min);

    }
}