E题为什么开滚动数组是就不对

#include<bits/stdc++.h>
using namespace std;

#define int long long
#define debug(x) cout << #x << " " << x << endl;

signed main()
{
    int n,K;
    cin >> n >> K;
    vector<int> a(n + 1);
    for(int i = 1;i <= n;i ++){
        cin >> a[i];
    }
    vector<vector<int>> dp(2,vector<int>(n + 1,-1e18));
    dp[0][0] = 0;
    dp[1][0] = 0;
    int ans = -1e18;
    for(int k = 1;k <= K;k ++){
        //cout << "____________________________________" << endl;
        //debug(k);
        for(int i = k;i <= k * 6;i ++){
            for(int j = 1;j <= min(6LL,i);j ++){
                dp[k & 1][i] = max(dp[k & 1][i],dp[k - 1 & 1][i - j] + a[i]);
            }
            //debug(dp[k & 1][i]);
        }
    }
    for(int i = 1;i <= n;i ++){
        ans = max(ans,dp[K & 1][i]);
    }
    cout << ans << endl;
    
}

但是不用滚动数组就对了

#include<bits/stdc++.h>
using namespace std;

#define int long long
#define debug(x) cout << #x << " " << x << endl;

signed main()
{
    int n,K;
    cin >> n >> K;
    vector<int> a(n + 1);
    for(int i = 1;i <= n;i ++){
        cin >> a[i];
    }
    vector<vector<int>> dp(K + 1,vector<int>(n + 1,-1e18));
    dp[0][0] = 0;
    int ans = -1e18;
    for(int k = 1;k <= K;k ++){
        //cout << "____________________________________" << endl;
        //debug(k);
        for(int i = k;i <= k * 6;i ++){
            for(int j = 1;j <= min(6LL,i);j ++){
                dp[k][i] = max(dp[k][i],dp[k - 1][i - j] + a[i]);
            }
            //debug(dp[k & 1][i]);
        }
    }
    for(int i = 1;i <= n;i ++){
        ans = max(ans,dp[K][i]);
    }
    cout << ans << endl;
    
}

求助