Coffee shops

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <stack>

using namespace std;

int arr[1000000];
int cost[1000000];
int is[1000000];

int main(int argc, char *argv[])
{
    ios::sync_with_stdio(0);
    int n = 0;
    cin >> n;

    for (int i = 0; i < n; ++i) {
        cin >> arr[i];
    }

    cost[0] = arr[0];
    is[0] = 1;

    if (n == 1) {
        cout << cost[0];
        return 0;
    }

    if (arr[1] < arr[0]) {
        cost[1] = arr[1];
        is[1] = 1;
    } else {
        cost[1] = cost[0];
        is[1] = 0;
    }

    for (int i = 2; i < n; ++i) {
        if (is[i - 1] == 0) {
            // not covered, we have to cover it
            cost[i] = cost[i - 2] + arr[i];
            is[i] = 1;
        } else {
            // covered, but we need to check if we can do better
            int cur_sum = arr[i] + cost[i - 2];

            if (cur_sum < cost[i - 1]) {
                // let's cover it with it
                cost[i] = cur_sum;
                is[i] = 1;
            } else {
                // no, we needn't cover it
                cost[i] = cost[i - 1];
                is[i] = 0;
            }
        }
    }

//    for (int i = 0; i < n; ++i)
//        cout << cost[i] << endl;

    cout << cost[n - 1];

    return 0;
}

Test 1

Verdict: UNKNOWN

Test 2

Verdict: UNKNOWN

Test 3

Verdict: UNKNOWN

Test 4

Verdict: UNKNOWN

Test 5

Verdict: UNKNOWN

Test 6

Verdict: UNKNOWN

Test 7

Verdict: UNKNOWN

Test 8

Verdict: UNKNOWN

Test 9

Verdict: UNKNOWN

Test 10

Verdict: UNKNOWN

Test 11

Verdict: UNKNOWN

Test 12

Verdict: UNKNOWN

Test 13

Verdict: UNKNOWN

Test 14

Verdict: UNKNOWN

Test 15

Verdict: UNKNOWN

Test 16

Verdict: UNKNOWN

Test 17

Verdict: UNKNOWN

Test 18

Verdict: UNKNOWN