POJ - 2228 Naptime（环形结构DP）

#include <iostream>
#include <cstring>
using namespace std;
const int N = 4000, INF = 0x3f3f3f3f;
int n,m,w[N],f[2][N][2];

void solve()
{
    for (int i = 2; i <= n; i ++ )
        for (int j = 0; j <= m; j ++ )
        {
            f[i & 1][j][0] = max(f[i - 1 & 1][j][0], f[i - 1 & 1][j][1]);
            f[i & 1][j][1] = -INF;
            if (j) f[i & 1][j][1] = max(f[i - 1 & 1][j - 1][0], f[i - 1 & 1][j - 1][1] + w[i]);
        }
}

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i ++ ) cin >> w[i];

    memset(f, -0x3f, sizeof f);
    f[1][0][0] = f[1][1][1] = 0;// 第n小时不在睡觉
    solve();
    int res = f[n & 1][m][0];
    
    memset(f, -0x3f, sizeof f);
    f[1][0][0] = 0,f[1][1][1] = w[1];// 第n小时在睡觉
    solve();
    res = max(res, f[n & 1][m][1]);
    
    cout << res << endl;
    return 0;
}