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)

object Main {
  def main(args: Array[String]): Unit = {
    solve
  }

  // 処理の方法はわかるけれど、全然整理できたコードにならない。。
  def solve(): Unit = {
    val sc = new java.util.Scanner(System.in)
    val n = sc.nextInt
    val v = new Array[Int](n)
    for (i <- 0 until n) {
      v(i) = sc.nextInt
    }

    val evenMap = scala.collection.mutable.Map[Int, Int]()
    for (i <- 0 until n by 2) {
      val num = v(i)
      if (evenMap.contains(num)) evenMap(num) += 1
      else evenMap(num) = 1
    }
    val evenList = evenMap.toList.sortBy(_._2).reverse

    val oddMap = scala.collection.mutable.Map[Int, Int]()
    for (i <- 1 until n by 2) {
      val num = v(i)
      if (oddMap.contains(num)) oddMap(num) += 1
      else oddMap(num) = 1
    }
    val oddList = oddMap.toList.sortBy(_._2).reverse

    val e1 = evenList(0)._1
    val e2 = if (evenList.size > 1) evenList(1)._1 else -1
    val o1 = oddList(0)._1
    val o2 = if (oddList.size > 1) oddList(1)._1 else -1

    if (e1 != o1) {
      println(n - evenMap(e1) - oddMap(o1))

    } else {
      println(math.min(
        (n - evenMap(e1) - oddMap.getOrElse(o2, 0)),
        (n - oddMap(o1) - evenMap.getOrElse(e2, 0)))
      )
    }
  }

}