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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>
 
int main(void) {
	int n;
 
 	scanf("%d", &n);
 
	int v[n];
	int guu[n / 2];
	int ki[n / 2];

	if(n < 2 || n > 100000 || n % 2 != 0) {
		exit(0);
	}

	if(n == 2) {
        printf("0");
        return (0);
    }

 
	for(int i = 0;i < n;i++) {
		scanf("%d", &v[i]);

		if(v[i] < 1 || v[i] > 100000) {
			exit(0);
		}

		if(i % 2 == 0) {
			guu[i / 2] = v[i]; 
		} else {
			ki[i / 2] = v[i];
		}
	}

	int guucount = 0;
	int kicount = 0;
	int guuhikaku = 0;
	int guuindex = 0;
	int kihikaku = 0;
	int kiindex = 0;
	int baka = 0;
	int aho = 0;
	int guflag = 0;
	int kiflag = 0;

	for(int i = 0;i < n / 2;i++) {

		for(int k = 0;k < i;k++) {
			if(guflag == 0 && guu[i] == guu[k]) {
				guflag = 1;
			}
			if(kiflag == 0 && ki[i] == ki[k]) {
				kiflag = 1;
			}
			if(guflag == 1 && kiflag == 1) {
				break;
			}
		}

		if(guflag == 1 && kiflag == 1) {
			guflag = 0;
			kiflag = 0;
			continue;
		}

		for(int j = 0;j < n / 2;j++) {

			if(guflag == 0 && guu[i] == guu[j]) {
				guucount++;
			}

			if(kiflag == 0 && ki[i] == ki[j]) {
				kicount++;
			}
		}

		if(guflag == 0 && guuhikaku < guucount) {
			baka = guuhikaku;
			guuhikaku = guucount;
			guuindex = i;
		}

		if(kiflag == 0 && kihikaku < kicount) {
			aho = kihikaku;
			kihikaku = kicount;
			kiindex = i;
		}

		guucount = 0;
		kicount = 0;
		kiflag = 0;
		guflag = 0;

	}

	if(guu[guuindex] == ki[kiindex]) {
		if(baka == aho) {
			printf("%d", n/2);
		} else if(baka > aho) {
			printf("%d", (n/2 - baka));
		} else {
			printf("%d", (n/2 - aho));
		}
	} else {
		printf("%d", ((n/2 - guuhikaku) + (n/2 - kihikaku)));
	}

	printf("\n");
}