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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict";

function main(input) {
  var lines = input.split('\n');
  var n = parseInt(lines.shift());
  var vs = splitNum(lines.shift()).slice(0, n);
  var map0 = new Array(1e5 + 1).fill(0).map(function (_, idx) {
    return {
      idx,
      count: 0
    };
  });
  var map1 = new Array(1e5 + 1).fill(0).map(function (_, idx) {
    return {
      idx,
      count: 0
    };
  });

  for (var i = 0; i < n; i += 2) {
    map0[vs[i]].count++;
    map1[vs[i + 1]].count++;
  }

  map0.sort(function (a, b) {
    return b.count - a.count;
  });
  map1.sort(function (a, b) {
    return b.count - a.count;
  });
  var result;

  if (map0[0].idx !== map1[0].idx) {
    // use different numbers.
    result = sumCount(map0.slice(1)) + sumCount(map1.slice(1));
  } else {
    // secondary
    var sum02 = sumCount(map0.slice(2));
    var sum12 = sumCount(map1.slice(2));
    var use0 = map0[1].count + sum02 + map1[0].count + sum12;
    var use1 = map0[0].count + sum02 + map1[1].count + sum12;
    result = Math.min(use0, use1);
  }

  console.log(result);
}

function sumCount(arr) {
  return arr.reduce(function (pv, _ref) {
    var count = _ref.count;
    return pv + count;
  }, 0);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));

function splitNum(line) {
  return line.split(/\s+/).map(function (n) {
    return parseInt(n);
  });
}