Card game

input/code.cpp: In function 'void Test()':
input/code.cpp:11:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   11 |     freopen("temp\\in.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
input/code.cpp: In function 'int main()':
input/code.cpp:17:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
input/code.cpp:19:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |         scanf("%d", &a[i]);
      |         ~~~~~^~~~~~~~~~~~~

#include<iostream>
#include<cstdio>
#include<algorithm>
typedef long long LL;

const int N=1e6+5;
int f[N], a[N];

void Test()
{
    freopen("temp\\in.txt", "r", stdin);
}
int main()
{
    // Test();
    int n;
    scanf("%d", &n);
    for(int i=1; i<=n; i++)
        scanf("%d", &a[i]);
    for(int i=3; i<=n; i++)
    {
        // when i is the last card that can't be fliped
        f[i] = std::max(f[i-1], f[i-3]+a[i-1]);
    }
    printf("%d", f[n]);

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED