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 Scala (2.11.7) (judge verdict: Accepted)

import java.util.Scanner

object Main {
    case class pseudoMap(key:Int , count:Int)
    implicit def tupleToName(tup: (Int, Int)): pseudoMap = tup match {
        case (key, count) => pseudoMap(key, count)
    }

    def main(args: Array[String]): Unit = {
        val scanner = new Scanner(System.in)
        val n: Int = scanner.nextInt
        val vs: List[Int] = List.fill(n)(scanner.nextInt)
        println(calc(vs))
    }

    def calc(nums: List[Int] ): Int ={
        val (evens, odds) = nums.zipWithIndex.partition(_._2 % 2 == 0)
        val (evensFirst, evensSecond) = take2MostOrder(evens.map(_._1))
        val (oddsFirst, oddsSecond) = take2MostOrder(odds.map(_._1))

        if (evensSecond.key == -1 && oddsSecond.key == -1){
          if (evensFirst.key != oddsFirst.key)
              0
          else
              nums.length / 2
        }
        else {
          if (evensFirst.key != oddsFirst.key)
              nums.length - evensFirst.count - oddsFirst.count
          else
            (nums.length - evensFirst.count - oddsSecond.count) min (nums.length - evensSecond.count - oddsFirst.count)
        }
    }

    def take2MostOrder(nums: List[Int]): ((Int,Int),(Int,Int)) = {
      val sortedNums: Seq[(Int, Int)] = nums.groupBy(n => n).mapValues(_.length).toSeq.sortBy(_.count).reverse
      (sortedNums(0), try{sortedNums(1)}catch{case e :Exception => (-1, Int.MinValue)})
    }
}