思路

线性dp

过程

代码

#include <iostream>

using namespace std;

typedef long long LL;

const int N = 1e5 + 10;
int n, a[N];
LL f[N];

int main()
{
    cin >> n;
    for(int i = 1;i <= n;i ++) cin >> a[i];
    for(int i = 3;i <= n;i ++)
        f[i] = max(f[i - 1], f[i - 3] + a[i - 1]);
    cout << f[n] << endl;
    return 0;
}